ART 268 3D Computer Graphics Texture Mapping and Rendering. Texture Mapping

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1 ART 268 3D Computer Graphics Texture Mapping and Rendering Texture Mapping Is the way in which a material is wrapped around an object. The default method is UVW mapping (see below). When you drag a material to an object, a texture tag is added to the object in the Object Manager. This tag has its specifies the settings for texture mapping, which can be modified in the Attributes Manager. Texture Mapping Methods There are several ways to apply materials to objects. These different methods provide ways to wrap and place materials on models so they look more convincing when rendered. Each mapping method takes the material s textures and projects them onto objects. The basic mapping modes are flat, cubic, cylindrical, and spherical mapping. CINEMA 4D adds several other modes that allow for greater flexibility. These are frontal, spatial, shrink- wrap, and UVW mapping. You can have more than one material assigned to an object in CINEMA 4D, each with different mapping modes. UVW Mapping (default): UVW Mapping is a way to pin a material onto an object. The material or texture is actually attached to the points of the object. So, if the object is deformed, the material moves and stretches with the points on the object. Since the material s distortion is directly linked to the underlying geometry of the object there is a direct relationship between the complexity of the model and the quality of the mapped results. In other words, a denser mesh on your model will result in better UVW mapping. This is perfect for skin and other organic surfaces. NOTE: UVW maps cannot be rotated or repositioned. Spherical Mapping: Spherical Mapping is like an elastic map of the world being stretched onto a globe. It is a little like cylindrical mapping, but to get the map to fit onto the virtual sphere it must be bunched or pinched at the poles since it all comes together at a point. Cylindrical Mapping: Cylindrical Mapping is like a label on a can of soup. A flat image is wrapped around and projected onto virtual cylinder. This virtual cylinder can be oriented and scaled in any way you want. Flat Mapping: Flat Mapping is like projecting a slide image onto an object. The image plane is always flat and you can either have the source be perpendicular to your object or at almost any angle, scale and direction. With flat mapping the 1

2 material is projected through the object and is visible on the backside of the object as well. This method is used to add labels or decals to objects. Typically materials are projected through objects and can be seen on both sides. By using the Front, Back, and Front & Back options you can control how materials are displayed. Generally Front & Back is fine and this choice is the default setting. For decals on an object use the Front or Back controls to apply materials. For example, if you wanted to make a playing card (made from a plane primitive) you would use front mapping for the front face of the card showing the value of the card, and back mapping for the back face of the card. This way you can have two separate materials on an object, without them interfering with each other. Cubic Mapping: Cubic Mapping is like having a slide projected onto each face of a cube. The same image is used for each face of the cube. Frontal Mapping: Frontal Mapping is like flat mapping except that it is applied only from the point of view of the active camera being used to render in CINEMA 4D. This means that there are some limits to the adjustments that can be made to how the map is projected. This technique is useful for certain special effects, but is generally not widely used. Spatial Mapping: Spatial Mapping is also like flat mapping except that it applied in a specific manner skewed through 3D space so that the smearing that one might associate with flat mapping is minimized. This is handy for applying stone and other organic materials to objects. Shrink Mapping: Shrink- wrap Mapping is a special way to map a material onto a virtual sphere. Unlike spherical mapping which pinches at both poles and along the top and bottom edges of the material, shrink- wrap mapping gathers the four corners of the map at one pole rather like wrapping a square piece of cloth onto a ball. There is some distortion to the map, but only at one of the poles. Camera Mapping : Camera Mapping is used to place 3D objects behind 2D images. Texture Tag Properties Selection Allows you to map different textures to different parts of the same object using a Selection Tag. Projection Mapping is the way in which a texture image is projected onto a surface. The surface is independent of the object surface but could have the same shape. It is the surface that is applied to an object, not the texture per se (see Materials handout for more information). 2

3 Side Allows you to choose whether a material faces inwards (Back), outwards (Front), or both. Mix Textures If more than one material is applied to an object then all the materials will be used. This option would need to be switched on for Decal Mapping. Tile used for infinite repetition of the texture image over an object s surface. Seamless used with tiling. Tiles are joined by mirroring them preventing seems. Use UVW for Bump undocumented, but I assume it means that UVW mapping will be applied to a materials Bump map if it has one. Offset U/V position of the texture image within its geometry. Length U/V size of the texture image (100% for both X and Y values covers the texture s geometry. Tiles U/V used to designate how many times a texture image is tiled within a texture. Repetitions U/V supposedly restricts the number of times a texture repeats within a UV space, but I can t get it to work. Texture Fitting Object Manager - > Tags Menu - > Fit to Object Resizes a selected texture to cover the object the texture is mapped to. To Fit a Texture to a Range of Polygons 1. Make the object editable (click on the Make Editable icon) 2. Select the polygon(s) to map to using the Live or other Selection tool. 3. Drag the material from the Materials Manage to those polygons using the Perspective View. Rendering Setting Options Below is a list of general rendering settings. Many more settings are available for more advanced rendering techniques. 3

4 Output For the output settings start with an option from the Preset menu. Click on the little arrow and select an option based needs. For this course we will be rendering for the Screen at 1440 x 900. This setting will provide us with a large image for portfolio use, the WWW. We do not need to make any other changes under Output for this course. Save Save when check a rendered file is automatically saved to the path below. File click the button with the three dots to designate a folder to save to; if you do not designate a saving location your render will not be saved to the hard disk. Format Tiff is fine for still images for animation you would select Quicktime Movie. Options button - only available for Quicktime Movie format and used to adjust the default settings. We do not need to make any other changes under Save for this course. Anti- aliasing Anti- aliasing None - disables antialiasing Geometry - smoothes object edges Best smoothes gradients in shadows and textures as well as object edges Filter sets the filter mode for antialiasing Cubic (Still Image) gives sharp edges to still images Gauss (Animation) blurs antialiasing to prevent flicker for film and video Mitchell high quality sharpening filter. Not documented. Sinc higher quality than Cubic, but slower to render. Not documented. For this course set Anti- aliasing to Best for final renders and leave on Geometry for test renders. The Filter can be left on the Cubic setting. 4

5 Effects Ambient Occlusion - determines to what degree each individual surface point in a scene is exposed and colors it accordingly. Apply to Project Switches on Ambient Occlusion. Color - Used to define the color gradient that AO assigns, dependent on exposure. Normally, it will be a simple custom black to white gradient. The left end of the gradient represents areas with minimal exposure (bottom of sphere) and the right side represents areas with maximum exposure. Be aware of the fact that these gradients will be treated as grayscale, depending on the material channel. Minimum Ray Length - Determines how the gradient defined in Color will be rendered between exposed and non- exposed areas. The closer the Minimum Ray Length value is to the Maximum Ray Length value, the further the gradient will be pushed towards the edges, which are defined by the maximum ray length. This value shouldn t really be tampered with. Leave it set to its default. Maximum Ray Length - Defines to which distance the surfaces see each other. If low values are used, the wall will not see the sphere and the image is rendered brighter. Where geometry meets, as with the floor and wall or the sphere and floor, even small rays will fall upon surfaces, which darkens those areas. If high values are used, a much larger distance will be included within which objects will be able to see each other, resulting in a softer, more homogeneous darkening that will cause longer render times. Lower values are recommended. Dispersion - During each AO calculation, several rays ( Samples ) will be emitted for each point within a virtual hemisphere in the scene. These samples check to see if any geometry lies within the Maximum Ray Length. Dispersion determines to what extent these samples will be taken into account on the hemisphere s surface. A value of 0% takes only the hemisphere s zenith (vertically over the sphere) into account. A value of 100% will take the entire hemisphere into account. How can this be applied in practice? Imagine Dispersion as blinders. The lower the value, the more the blinders close and the more the sample area will be limited to the vertical. Accuracy - Determines where and in what amount samples must be distributed in order to achieve the best possible result. In critical areas, samples to the amount of Maximum Samples will be used. Hence, the Accuracy setting has the most influence in critical areas (since higher values in these areas lead to more samples) and less influence in less critical areas, which use the Minimum Samples value. 5

6 Minimum Samples - Use this setting to define the number of samples that should be used in less critical areas. Maximum Samples - Use this setting to define the number of samples that should be used in critical areas. The exact number of samples will be dispersed dynamically in correlation to the Accuracy setting. Contrast - Use this setting to adjust the AO effect s contrast. Negative values can also be entered. Use Sky Environment - If AO is used in the Diffusion material channel, a separate light source must be used. AO also works without a light source if the Sky object is used as Illumination. If Use Sky Environment is active, the reflected sky color will be multiplied onto the final AO image. To do this, AO must be placed into the Environment or Luminance material channels. Evaluate Transparency - When active, transparency will be analyzed on the basis of the Transparency or Alpha material channels. In doing so, the degree of transparency will be taken into consideration: A semi- transparent sphere will still cause some AO in spite of this option being active. Self Shadowing Only - When active, separate objects will not see each other, they will only see themselves. Caustics Caustics are patterns of focused light created by curved surfaces that are reflective/refractive the curvature of the surfaces focuses the light. Caustic effects add to the photo- realism of a scene at the cost of increased rendering times. Surface Caustics show up on object surfaces only Volume Caustics used with volumetric lighting and are visible as they pass through the air Strength brightness of the caustic effect Step Size used with volume caustics to calculate how often photons are recorded; lower values are higher quality and take longer to render. Only available for volume caustics. Sample Radius - used with volume caustics to calculate the distance between photon interpolation; higher values are higher quality and take longer to render. Only available for volume caustics. Samples - used with volume caustics to as the number of photons used to calculate the caustics effect; higher values are higher quality and take longer to render. Only available for volume caustics. Recompute First Time - calculates caustics settings only for the first render Always calculates caustics settings for every render Never ignores caustics settings Save Solution saves caustics calculations at render time for future renders Single Animation Solution used for calculating caustics based on scenes that use camera animation. For example, a camera- based. 6

7 Cel Renderer creates cartoon- style images Color - renders only visible surfaces, but with reduced color palette to create a cartoon- like image; deselected, renders only visible surfaces with black lines drawn on a white background Illumination - the shading of object is affected by illumination Outline - draws an outline around the silhouette of objects Edges - surrounds polygon edges with a thin black line, unless an edge color has been specified Edge Color - allows you to specify a color for edge coloring Background Color - allows you to specify a color for background color when Color is disabled Quantize set the number of different levels of color for color reduction; higher settings give smoother gradients Steps number of color steps for quantization Color Correction adjusts the color balance of the image Color Mapping used to balance color with brightness when Global Illumination has been applied. Cylindrical Lens used to supply a scene to matte painters to create background mattes from. Depth of Field renders camera depth of field if used by cameras Global Illumination Improves the photo- realism of renders by adding indirect light to a scene - renders light reflecting around a scene at the cost of increased rendering times General Tab GI Mode IR (Still Image): Your scene is not animated or you only want to render a single frame of an animation. IR (Camera Animation): You have animated a camera; objects and lights are not animated. QMC : Indoor/outdoor (most precise but very slow GI rendering; always grainy unless very high values are used): IR+QMC (Still Image): Outdoor (primarily illuminated by the sky; possible additional illumination; light should be reflected multiple times) IR+QMC (Camera Animation): You have animated a camera (primarily illuminated by the sky; possible additional illumination; light should be reflected multiple times); objects and lights are not animated. IR+QMC (Full Animation): This mode must be used if lights and/or objects have been animated (the camera can, of course, also be animated). Generates absolute flicker- free animations with moderate render times. 7

8 IR+QMC (NET Render): Same as the previous mode with the exception that this mode should be used when rendering across a network. Sky Sampler : Outdoor (illuminated by the sky only; reflected light not important; precise HDRI shadows). Diffuse Depth Diffuse Depth defines the number of times light reflects in a scene, i.e. how often a "ray of light" is reflected from surfaces. The minimum Diffuse Depth value of 1 results in only a direct illumination via flat, light- emitting elements (such as GI Portals or Polygon Lights). A Diffuse Depth value of 2 is required to achieve an indirect illumination, i.e. light reflected from other surfaces. Greater Diffuse Depth values will result in correspondingly, but moderately, longer render times (the difference between a value of 1 and 2 is greater than that between 2 and 8) but the dispersion of light will become increasingly homogeneous, brighter and more realistic. However, the effect at values greater than 3 in a normal scene will become less and less noticeable and the rendered result will simply become brighter. Primary/Secondary Intensity - Use these parameters to adjust the GI brightness based on the number of light reflections. The Primary Intensity parameter affects the regions being illuminated directly; the Secondary Illumination parameter affects reflected light. Gamma - This gamma value only affects the indirect GI lighting. Gamma values define how the internally rendered brightness values should be displayed in RGB mode. Simply stated, a progression from the darkest (black) to brightest (white) is defined. This lets relatively dark renderings (e.g. resulting from a low Diffuse Depth value) be brightened. But be careful - high gamma values will reduce contrast and "flatten" the overall image (values ranging from 1 to 3 have proven to be most effective; in some instances higher values may be necessary). Values less than 1 will darken the image, whereas values greater than 1 will brighten an image (see example above). Glow Applies a hazy glow effect to an entire scene. Hair Render gives advanced control over the settings for rendering hair. Highlights used to add lens flares to highlights. Lens Effects renders light lens effects if used by lights. Median Filter flattens high contract pixel color values based on the Strength setting. Object Glow renders material glow effects if applied to materials. Remote opens rendered frames in another application for post- editing. 8

9 Sharpen Filter sharpens an image to a degree based on the Strength setting. Sketch and Toon used to create comic- book like renders and other drawn effects. Soft Filter softens an image to a degree based on the Strength setting. Sub- Frame Motion Blur used to simulate a camera panning swiftly. Vector Motion Blur - Vector Motion Blur is based both on an object s speed as well as the shutter angle of the camera itself. Watermark lets you add copyright and other information to an image at render time. 9