Material Definition Language Handbook

Transcription

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6 Material Definition Language Handbook

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8 Outline 1 The design rationale for MDL 2 The structure of a material 3 Light at a surface 4 Fabric a modular approach

9 1 The design rationale for MDL

10 red plastic ball render picture Object and appearance together

11 plastic ball render picture red Separate appearance attribute

12 ball render picture red plastic Separate appearance

13 ball render picture red plastic Attribute as appearance parameter

14 bicycle render picture red plastic A different object

15 bicycle bicycle render picture render picture red plastic blue plastic A different attribute

16 bicycle bicycle bicycle render picture render picture render picture red plastic blue plastic blue metal A different substance

17 geometry render picture parameters material The general categories

18 geometry render picture MDL parameters material The domain of MDL

19 Object (Le Déjeuner en fourrure) Méret Oppenheim, 1936

20 Two big ideas

21 Idea #1: Light is only reflected, transmitted and emitted.

22 Reflection, transmission and emission

23 Reflection and refraction

24 Emission

25 Volume effects

26 Idea #2: Angles matter.

27 A perfectly specular surface

28 A perfectly diffuse surface

29 Surfaces of increasing roughness resulting in decreasing glossiness

30 Examples of the distribution function

31 Varying brightness based on the angle of view with a constant light angle

32 Varying brightness based on the incident angle of light with a constant view angle

33 The effect of increasing surface roughness on transmission

34 A normal vector forms a 90-degree angle to the surface

35 The normal vector creates a frame of reference for the viewing and lighting angles

36 The normal vector describes the orientation of a surface at any point

37 reflection transmission emission diffuse plaster frosted plexiglas heated iron glossy brushed aluminum shower door glass spotlight specular mirror crystal ball laser (?) Examples of the combinations of light interaction and angular dependence?

38 Material Surface Reflection and transmission Emission Volume scattering Geometric manipulation The structural model of an MDL material

39 An MDL material is a grouping of rendering properties based both on the physics of light as well as on practical and traditional techniques that extend the power of the renderer.

40 2 The structure of a material

41 A model of compound data

42 Data type: circle number number number cx cy radius A data compound type

43 Data type: circle number cx. number number cy radius A data compound type

44 Data type: circle A circle instance: circle_1 number cx cx 0. number number cy radius cy 0 radius 5 A compound type and an instance of the type

45 Data type: color number number number red green blue A compound data type

46 Data type: color number red. number number green blue A compound data type

47 Data type: color A color instance: dark_red number red red 0.5. number number green blue green 0.1 blue 0.2 A compound type and an instance of the type

48 Data type: tinted_circle number number number color cx cy radius tint A compound data type

49 Data type: tinted_circle number number number color cx cy radius tint. A compound data type

50 Data type: tinted_circle number cx number cy. A tinted_circle instance: dark_red_circle cx 0 cy 0 radius 5 number color radius tint tint A color instance red 0.5 green 0.1 blue 0.2 A doubly compound type and an instance of the type

51 The syntax of compound data in MDL

52 struct circle { float cx; float cy; float radius; }; Syntax of struct declaration

53 struct circle { float cx; float cy; float radius; }; Syntax of struct declaration

54 struct circle { float cx; float cy; float radius; }; struct struct-name {... }; type field-name ; Syntax of struct declaration

55 struct-name ( field-value,... ) Creating an instance of an MDL struct

56 struct-name ( field-value,... ). Creating an instance of an MDL struct

57 struct-name ( field-value,... ). circle(0, 0, 5) Creating an instance of an MDL struct

58 struct color { float red; float green; float blue; }; A struct declaration

59 struct color {. float red; float green; float blue; }; A struct declaration

60 struct color { float red; float green; float blue; }; color(0.5, 0.1, 0.2). An instance created from the struct type

61 Defining default values for the fields of a struct

62 struct struct-name { type field-name = default-value ;... }; Defining default values for the fields of a struct

63 struct struct-name { type field-name = default-value ;.... }; Defining default values for the fields of a struct

64 struct struct-name { type field-name = default-value ;... };. struct circle { float cx = 0.0; float cy = 0.0; float radius = 1.0; }; Defining default values for the fields of a struct

65 struct-name ( field-name: field-value ) struct-name ( field-name-1: field-value-1, field-name-2: field-value-2,... ) Name/value pairs in the argument list

66 struct-name ( field-name: field-value ). struct-name (. field-name-1: field-value-1, field-name-2: field-value-2,... ) Name/value pairs in the argument list

67 struct-name ( field-name: field-value ). circle(radius: 5.0) struct-name ( field-name-1: field-value-1, field-name-2: field-value-2,... ). circle(radius: 5.0, cx: 5, cy: 15) Creating an instance of the circle type

68 struct tinted_circle { float cx = 0.0; float cy = 0.0; float radius = 1.0; color tint = color( 0.5, 0.5, 0.5); }; A doubly compound type

69 struct tinted_circle { float cx = 0.0; float cy = 0.0; float radius = 1.0;. color tint = color( 0.5, 0.5, 0.5); }; A doubly compound type

70 struct tinted_circle { float cx = 0.0; float cy = 0.0; tinted_circle( 2, 4, 10, color(0.5, 0.1, 0.2)); float radius = 1.0;. color tint = color( 0.5, 0.5, 0.5); tinted_circle( tint: color( 1, 0, 0)) }; Creating an instance of the tinted_circle type

71 tinted_circle ( cx: 2, cy: 4, radius: 5, tint: color ( red: 0.5, green: 0.1, blue: 0.2 )); Formatting the code of compound types

72 The design of the MDL material type

73 Material Reflection properties Transmission properties Emission properties Fundamental surface interaction properties

74 Material Surface properties Reflection Transmission Emission Surface interaction properties grouped together

75 Material Surface properties Reflection Transmission Emission Volume properties Adding volumetric properties

76 Material Surface properties Reflection Transmission Emission Volume properties Geometric properties Adding geometric properties

77 Material Surface properties of front-facing surfaces Reflection Transmission Emission Surface properties of back-facing surfaces Reflection Transmission Emission Volume properties Geometric properties Adding a field for the appearance of back-facing surfaces

78 Material Surface properties of front-facing surfaces Reflection Transmission Emission Surface properties of back-facing surfaces Reflection Transmission Emission Volume properties Geometric properties Shared properties Index of refraction Surface treated as boundary or volume Adding shared properties

79 struct material { uniform bool thin_walled = false; material_surface surface = material_surface(); material_surface backface = material_surface(); uniform color ior = color(1.0); material_volume volume = material_volume(); material_geometry geometry = material_geometry(); }; The material struct

80 Material properties and distribution functions

81 struct material { uniform bool thin_walled = false; material_surface surface = material_surface(); material_surface backface = material_surface(); Surface interaction uniform color ior = color(1.0); material_volume volume = material_volume(); Volumetric effects material_geometry geometry = material_geometry(); Geometric manipulation }; The material struct

82 bsdf Reflection and transmission The distribution function (DF) types

83 Appearance dependent upon viewing angle Appearance dependent upon lighting angle The bidirectional aspect of the BSDF

84 bsdf Reflection and transmission The distribution function (DF) types

85 bsdf edf Reflection and transmission Emission The distribution function (DF) types

86 bsdf edf vdf Reflection and transmission Emission Volume The distribution function (DF) types

87 Reflection and transmission Emission Volume diffuse_reflection_bsdf diffuse_edf anisotropic_vdf diffuse_transmission_bsdf specular_bsdf spot_edf measured_edf simple_glossy_bsdf backscattering_glossy_reflection_bsdf measured_bsdf The standard distribution functions

88 struct material_surface { bsdf scattering = bsdf(); Bidirectional scattering DF material_emission emission = material_emission(); }; The struct describing surface interaction properties

89 struct material_surface { bsdf scattering = bsdf(); material_emission emission = material_emission(); Light emission property }; The struct describing surface interaction properties

90 struct material_emission { edf emission = edf(); Light emission DF color intensity = color(0.0); intensity_mode mode = intensity_radiant_exitance; }; The struct describing emissive properties

91 struct material_volume { vdf scattering = vdf(); Volume DF color absorption_coefficient = color(); color scattering_coefficient = color(); }; The struct describing volumetric properties

92 struct material_geometry { float3 displacement = float3(0.0); float cutout_opacity = 1.0; float3 normal = state::normal(); }; The struct describing geometric properties

93 material thin_walled surface scattering emission backface scattering emission ior material ( thin_walled : boolean-value, ) surface backface ior volume geometry : material-surface-instance, : material-surface-instance, : color-instance, : material-volume-instance, : material-geometry-instance volume scattering geometry

94 2 Light at a surface

95 The simplest material

96 material() The simplest material

97 Material property material_surface material_emission material_volume material_geometry Effect of its default value No reflection or transmission of light No emission of light No absorption or scattering of light in the volume No manipulation of the surface Visual effect of the default values of the material properties

98 material nil() = material(); Creating a material definition from the simplest material

99 declaration = definition ; Syntax of a material creation

100 material name(material-parameters) = material(material-arguments); Syntax of arguments and parameters

101 material name ( material-parameters ) = material ( material-arguments ); Formatting a material definition

102 The compound structure of a diffuse reflection material

103 material instance material properties distribution functions A model of the nesting of data in an MDL material

104 material plaster () = material ( material-arguments ); Defining a material named plaster

105 material plaster () = material ( surface: surface-property ); Adding the surface field

106 material plaster () = material ( surface: material_surface ( material-surface-arguments )); Using the material_surface property

107 material plaster () = material ( surface: material_surface ( scattering: bsdf-instance )); Adding the scattering field to the material_surface property

108 material plaster () = material ( surface: material_surface ( scattering: df::diffuse_reflection_bsdf ( bsdf-arguments ))); Using the diffuse reflection BSDF

109 material plaster () = material ( surface: material_surface ( scattering: df::diffuse_reflection_bsdf ( tint: color(0.7) ))); The definition of the plaster material

110 The appearance of diffuse reflection produced by the plaster material

111 material thin_walled surface scattering emission backface scattering emission material plaster () = material ( surface: material_surface ( scattering: df::diffuse_reflection_bsdf ( tint: color(0.7) ))); ior volume scattering geometry

112 The material's role in the rendering system

113 material plaster () = material ( surface: material_surface ( scattering: df::diffuse_reflection_bsdf ( tint: color(0.7) ))); The plaster material defines no parameters

114 plaster() No arguments can be supplied to the plaster material

115 material plaster ( parameter-declarations ) = material ( surface: material_surface ( scattering: df::diffuse_reflection_bsdf ( parameter-references ))); Adding parameters to the plaster material

116 material plaster ( color tint = color(0.7) ) Tint exposed as a parameter = material ( surface: material_surface ( scattering: df::diffuse_reflection_bsdf ( tint: tint ))); Using the tint parameter value Exposing the tint parameter in the interface

117 plaster(tint: color(0.3, 0.1, 0.1)) Using the plaster material with a value for the tint argument

118 material plaster ( color tint = color(0.7), float roughness = 0.0 ) Degree of roughness as a parameter = material ( surface: material_surface ( scattering: df::diffuse_reflection_bsdf ( tint: tint, roughness: roughness ))); Roughness passed to the BSDF Exposing the roughness parameter in the interface

119 Diffuse transmission

120 material diffuse_transmission () = material ( surface: material_surface ( scattering: df::diffuse_transmission_bsdf ( tint: color(1.0) ))); Diffuse transmission A simple material for diffuse transmission

121 Diffuse transmission

122 Diffuse transmission through a thin object

123 Shadows visible from diffuse transmission through a thin object

124 Light emission

125 material thin_walled surface scattering emission backface scattering emission ior material emission ( color tint = color(1.0) ) = material ( surface: material_surface ( emission: material_emission ( emission: df::diffuse_edf(), intensity: tint ))); Light emission from front surface volume scattering geometry

126 Emissive rectangular polygons

127 material thin_walled surface scattering emission backface scattering emission ior volume scattering material emission_with_diffuse_backface ( color tint = color(1), color backtint = color(.8,.78,.75) ) = material ( thin_walled: true, surface: material_surface ( emission: material_emission ( emission: df::diffuse_edf(), intensity: tint )), backface: material_surface ( scattering: df::diffuse_reflection_bsdf ( tint: backtint ))); Light emission from front surface Diffuse reflection from back surface geometry

128 Emission from the front of the polygon, diffuse reflection from the back

129 Lighting environment of the images of the previous section

130 Emissive objects of the previous image pointing down

131 Emissive objects of the previous image pointing up

132 Specular interaction at a surface

133 bsdf specular_bsdf ( color tint = color(1.0), uniform scatter_mode mode = df::scatter_reflect Scattering mode ); The reflection mode of the specular BSDF

134 enum scatter_mode { scatter_reflect, scatter_transmit, scatter_reflect_transmit }; The three scatter modes

135 material thin_walled surface scattering emission backface scattering emission material mirror () = material ( surface: material_surface ( scattering: df::specular_bsdf ( tint: color(0.5), mode: df::scatter_reflect ))); Specular reflection ior volume scattering geometry

136 Pure specular reflection

137 Lighting environment of previous image

138 Effect of different lighting environment on the specular surfaces

139 Close-up of previous image

140 Small emissive surfaces pointing toward the ceiling

141 Close-up of bounce-light from ceiling

142 Specular transmission at a surface

143 Specular transmission

144 material specular_transmission ( color tint = color(1) ) = material ( ior: color(1.3), surface: material_surface ( scattering: df::specular_bsdf ( tint: tint, mode: df::scatter_transmit ))); Transmission mode A specular transmission material

145 Modifying the transmissive color

146 Hue effects of transmissive color

147 Combining specular reflection and transmission

148 Glossy interaction

149 Glossy reflection

150 Glossy transmission

151 Combining glossy reflection and transmission

152 Lighting techniques

153 diffuse reflection emission Surrounding an emissive surface with a diffuse reflection surface

154 Emissive surfaces contained within a non-emissive objects

155 Specular reflections using a sun and sky simulation

156 Close-up of sun and sky simulation

157 4 Fabric a modular approach

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160 From A Practical Microcylinder Appearance Model for Cloth Rendering, Iman Sadeghi et al., 2013

161 From A Practical Microcylinder Appearance Model for Cloth Rendering, Iman Sadeghi et al., 2013

162 From A Practical Microcylinder Appearance Model for Cloth Rendering, Iman Sadeghi et al., 2013

163 From A Practical Microcylinder Appearance Model for Cloth Rendering, Iman Sadeghi et al., 2013

164 From A Practical Microcylinder Appearance Model for Cloth Rendering, Iman Sadeghi et al., 2013

165 A fabric material in MDL

166 o warp o weft

167 highlight (warp) highlight layering (iridescence) highlight layering (weft) layering (thin silk) translucency highlight Relationship of the components in the fabric material design

168 Combining distribution functions

169 Simple car paint material with clear coat

170 Layers: diffuse, edge coloring, broad highlight, narrow highlight, clear coat

171 All layers

172 normalized_mix Weights normalized if sum greater than 1.0 clamped_mix Weights added until greater than 1.0, then clamped Mixing distribution functions

173 weighted_layer fresnel_layer custom_curve_layer measured_curve_layer Add layer based on weight factor Add layer according to the index of refraction Add layer based on directionally dependent function Add layer based on a measured reflectance curve Layering distribution functions

174 Defining the warp layer

175 material anisotropic_glossy ( color tint = color(0.7), float roughness_u = 1.0, float roughness_v = 0.15) = material ( surface: material_surface ( scattering: df::simple_glossy_bsdf ( Glossy distribution tint: tint, roughness_u: roughness_u, roughness_v: roughness_v, Anisotropic effect mode: df::scatter_reflect))); Definition of the warp reflection

176 anisotropic_glossy ( tint: color(0.3,0.22,0.3), roughness_v: 0.3)

177 Defining the weft layer

178 Module std df state math tex limits anno Functionality Imports all other standard modules and re-exports all declarations Elemental distribution functions, modifiers, and combiners Renderer state functions Library math functions and constants Library texture functions Global constants Annotations MDL standard modules

179 float3 modify_normal_u(float factor = 1.0) { return math::normalize( state::normal() Take the normal vector + state::texture_tangent_u(0) and push it over * factor); by some amount. } Modifying the surface normal for multiple highlights in the weft

180 material parameters field values A material s field values can refer to the material s parameters

181 material material parameters parameters temporary variables field values field values Temporary variables define intermediate values for use in the field values

182 material material material parameters material name ( parameters ) = parameters field values temporary variables let { } variables field values material ( ) field values The syntax of the three primary structural components of a material

183 material material name ( parameters ) = let { } variables material ( ) field values

184 material name ( parameters ) = let { variables } material ( ) material field values material anisotropic_glossy_three_lobes ( color tint = color(0.7), float roughness = 0.1, uniform float normal_strength = 1.5) = let { float3 start_normal = modify_normal_u(-normal_strength); float3 middle_normal = state::normal(); float3 end_normal = modify_normal_u(normal_strength); bsdf glossy_component = anisotropic_glossy ( tint: tint, roughness_v: 1, roughness_u: roughness).surface.scattering; } in material ( surface: material_surface ( scattering: df::weighted_layer ( weight: 0.5, normal: middle_normal, layer: glossy_component, base: df::weighted_layer ( weight: 0.5, normal: end_normal, layer: glossy_component, base: df::weighted_layer ( weight: 1.0, normal: start_normal, layer: glossy_component)))));

185 material anisotropic_glossy_three_lobes ( color tint = color(0.7), float roughness = 0.1, uniform float normal_strength = 1.5) = let { float3 start_normal = modify_normal_u(-normal_strength); float3 middle_normal = state::normal(); float3 end_normal = modify_normal_u(normal_strength); bsdf glossy_component = anisotropic_glossy ( tint: tint, roughness_v: 1, roughness_u: roughness).surface.scattering; } in material ( surface: material_surface ( scattering: df::weighted_layer ( weight: 0.5, normal: middle_normal, layer: glossy_component, base: df::weighted_layer ( weight: 0.5, normal: end_normal, layer: glossy_component, base: df::weighted_layer ( weight: 1.0, normal: start_normal, layer: glossy_component))))); Signature Temporary variables Field values

186 material anisotropic_glossy_three_lobes (... ) = let { float3 start_normal = modify_normal_u(-normal_strength); float3 middle_normal = state::normal(); float3 end_normal = modify_normal_u(normal_strength); bsdf glossy_component = anisotropic_glossy ( tint: tint, roughness_v: 1, roughness_u: roughness).surface.scattering; } in material ( surface: material_surface ( scattering: df::weighted_layer ( weight: 0.5, normal: middle_normal, layer: glossy_component, base: df::weighted_layer ( weight: 0.5, normal: end_normal, layer: glossy_component, base: df::weighted_layer ( weight: 1.0, normal: start_normal, layer: glossy_component))))); Layer Layer Layer

187 material anisotropic_glossy_three_lobes (... ) = let { float3 start_normal = modify_normal_u(-normal_strength); float3 middle_normal = state::normal(); float3 end_normal = modify_normal_u(normal_strength); bsdf glossy_component = anisotropic_glossy ( tint: tint, roughness_v: 1, roughness_u: roughness).surface.scattering; } in material ( surface: material_surface ( scattering: df::weighted_layer ( weight: 0.5, normal: middle_normal, layer: glossy_component, base: df::weighted_layer ( weight: 0.5, normal: end_normal, layer: glossy_component, base: df::weighted_layer ( weight: 1.0, normal: start_normal, layer: glossy_component))))); Bend the normal vector one way Leave it alone Bend it the other way Unmodified normal vector Modified normal vector Modified normal vector

188 anisotropic_glossy_three_lobes ( tint: color(0.2,0.3,0.2), roughness: 0.15)

189 const color magenta = color(.3,.22,.3); const color green = color(.20,.3,.2); Defining constants for named colors

190 material warp_and_weft ( color warp_color = magenta, float warp_roughness = 0.3, color weft_color = green, float weft_roughness = 0.15, uniform float weft_normal_strength = 1.5, uniform float warp_to_weft = 3, float shadowing = 0.0) Warp control Weft control Warp contribution Shadowing Signature of material warp_and_weft

191 material warp_and_weft (... ) = let { bsdf warp = anisotropic_glossy ( tint: warp_color, roughness_u: 1.0, roughness_v: warp_roughness).surface.scattering; bsdf weft = anisotropic_glossy_three_lobes ( tint: weft_color, roughness: weft_roughness, normal_strength: weft_normal_strength).surface.scattering; float warp_weight = warp_to_weft > 1? / warp_to_weft : warp_to_weft; } in material ( surface: material_surface ( scattering: df::custom_curve_layer ( weight: shadowing, normal_reflectivity: 0.05, grazing_reflectivity: 1.0, exponent: 3, base: df::weighted_layer ( weight: warp_weight, layer: weft, base: warp)))); Layer against black (default) for shadowing Combine warp and weft layers

192 material warp_and_weft (... ) = let { bsdf warp = anisotropic_glossy ( tint: warp_color, roughness_u: 1.0, roughness_v: warp_roughness).surface.scattering; bsdf weft = anisotropic_glossy_three_lobes ( tint: weft_color, roughness: weft_roughness, normal_strength: weft_normal_strength).surface.scattering; float warp_weight = warp_to_weft > 1? / warp_to_weft : warp_to_weft; } in material ( surface: material_surface ( scattering: df::custom_curve_layer ( weight: shadowing, normal_reflectivity: 0.05, grazing_reflectivity: 1.0, exponent: 3, base: df::weighted_layer ( weight: warp_weight, layer: weft, base: warp)))); Calculate the warp layer Calculate the weft layer Calculate the warp contribution factor Use the warp contribution factor Use the warp layer Use the weft layer

193 warp_and_weft ( warp_color: color(0.3,0.22,0.3), weft_color: color(0.2,0.3,0.2))

194 material translucency ( color transmission_color = color(1)) = material ( thin_walled: true, surface: material_surface ( scattering: df::diffuse_transmission_bsdf ( tint: transmission_color))); Scattering by transmission A reusable material for translucency

195 translucency()

196 material iridescent_silk ( color warp_color = magenta, float warp_roughness = 0.3, color weft_color = green, float weft_roughness = 0.15, uniform float weft_normal_strength = 1.5, uniform float warp_to_weft = 3, float transmission_weight = 0.2, color transmission_color = color(0.95,1.0,0.95), float transmission_exponent = 3.0, float shadowing = 0.0) Warp control Weft control Warp contribution Transmission control Shadowing Signature of material iridescent_silk

197 material iridescent_silk (... ) = let { bsdf glossy = warp_and_weft ( warp_color: warp_color, warp_roughness: warp_roughness, weft_color: weft_color, weft_roughness: weft_roughness, weft_normal_strength: weft_normal_strength, warp_to_weft: warp_to_weft, shadowing: shadowing).surface.scattering; bsdf translucent = translucency ( transmission_color: transmission_color).surface.scattering; } in material ( thin_walled: true, surface: material_surface ( scattering: df::custom_curve_layer ( weight: 1.0, normal_reflectivity: transmission_weight, grazing_reflectivity: 1.0, exponent: transmission_exponent, layer: glossy, base: translucent))); Glossiness calculation Translucency calculation Layering function Glossy layer Translucent base

198 iridescent_silk()

199 iridescent_silk(transmission_weight: 0.5)

200 iridescent_silk ( warp_color: color(0.2,0.3,0.6), weft_color: color(0.07,0.05,0.05), transmission_color: color(0.95,0.95,1), transmission_weight: 0.05, shadowing: 0.3, warp_roughness: 0.3, weft_roughness: 0.15)

201 iridescent_silk ( warp_color: color(0.2,0.3,0.6), weft_color: color(0.07,0.05,0.05), transmission_color: color(0.95,0.95,1), transmission_weight: 0.05, shadowing: 0.3, warp_roughness: 0.3, weft_roughness: 0.15)

202 Other examples (and the future)

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