Shader Programming 1. Examples. Vertex displacement mapping. Daniel Wesslén 1. Post-processing, animated procedural textures

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1 Shader Programming 1 Examples Daniel Wesslén, dwn@hig.se Per-pixel lighting Texture convolution filtering Post-processing, animated procedural textures Vertex displacement mapping Daniel Wesslén 1

2 Fragment Mandelbrot set Animation Direct volume rendering Isosurface extraction Fur Crysis Daniel Wesslén 2

3 Crysis Age of Conan OpenGL 1.4 (2002) connectivity The OpenGL pipeline vertex transform & lighting primitive assembly rasterization texture fog, texturing output copy OpenGL 2.1 (2006) OpenGL FBO + GeForce 8 connectivity connectivity vertex primitive assembly rasterization vertex primitive assembly rasterization texture fragment geometry fragment buffer object copy vertexindexpixel- output buffer object vertexindexpixeltextureuniform- texture copy output Daniel Wesslén 3

4 CPU CPU Shader processing RAM Parallel processing Vertex vertices: properties vertex scheduler vertex processors vertices: properties vertices: positions, properties fragment processors vertex processors rasterizer vertices: positions, properties fragments: positions, properties fragments: colors Transform Animation Per-vertex lighting Displacement Mostly: Parameter setup for fragments Can not modify topology No access to other vertices Fragment fragments: positions, properties Parallel processing fragment processors fragments: colors vertex scheduler rasterizer Per-pixel lighting Texturing Compositing Filtering Fog Can not read or write pixels No access to other fragments vertexgeometry- primitive assembly fragment- Daniel Wesslén 4

5 Simple example Per-pixel lighting Vertex Vertex uniform (prog. to vertex, per primitive) attribute (prog. to vertex, per vertex) varying (vertex to fragment) Vertex Vertex int, float, bool (basic types) vec2, vec3, vec4 (2,3,4d vector) mat2, mat3, mat4 (2,3,4d float matrix) ivec3, bvec4, etc. (vectors only) Daniel Wesslén 5

6 Vertex vertex built-in attributes writing to gl_position is mandatory Vertex built-in uniforms Fragment Fragment uniform float shininess; uniform float shininess; built-in functions vec3 nlight = normalize(gl_lightsource[0].position.xyz - pos); vec3 neye = normalize(-pos); vec3 nnormal = normalize(normal); vec3 nhalf = normalize(neye + nlight); float diff = max(0.0, dot(nlight, nnormal)); float spec = diff > 0.0? pow(dot(nhalf, nnormal), shininess) : 0.0; vec3 nlight = normalize(gl_lightsource[0].position.xyz - pos); vec3 neye = normalize(-pos); vec3 nnormal = normalize(normal); vec3 nhalf = normalize(neye + nlight); float diff = max(0.0, dot(nlight, nnormal)); float spec = diff > 0.0? pow(dot(nhalf, nnormal), shininess) : 0.0; gl_fragcolor = vec4(color * diff + spec, 1); gl_fragcolor = vec4(color * diff + spec, 1); Fragment uniform float shininess; writing to gl_fragcolor or gl_fragdata[] is mandatory vec3 nlight = normalize(gl_lightsource[0].position.xyz - pos); vec3 neye = normalize(-pos); vec3 nnormal = normalize(normal); vec3 nhalf = normalize(neye + nlight); float diff = max(0.0, dot(nlight, nnormal)); float spec = diff > 0.0? pow(dot(nhalf, nnormal), shininess) : 0.0; gl_fragcolor = vec4(color * diff + spec, 1); Daniel Wesslén 6

7 Derived from C No pointers, strings or characters No promotion (sort of) Function overloading Storage types No static uniform, attribute, varying No #include (not file based) New types Vectors vec2, ivec3, bvec4, etc. Swizzling (vector.xz, color.rgb) Matrices mat2, mat3, mat4 Samplers For sampling textures sampler2d, sampler3d, samplerrect Vector operations Swizzling Pick components vec3(1,2,3).zyxz == vec4(3,2,1,3) Operators v * u, v + u, v / 2.0, etc. Per-component ops Functions dot(v,u), cross(v,u), normalize(v), etc. Texturing Samplers Representing texture units uniform sampler2d diffuse; Sampling Functions for reading from a sampler vec4 color = texture2d(diffuse, texcoord); Daniel Wesslén 7