Shader Programming. Daniel Wesslén, Stefan Seipel, Examples

Transcription

1 Shader Programming Daniel Wesslén, Stefan Seipel, Examples 1

2 Per-pixel lighting Texture convolution filtering 2

3 Post-processing, animated procedural textures Vertex displacement mapping 3

4 Fragment shader Mandelbrot set Animation 4

5 Direct volume rendering The OpenGL pipeline 5

6 OpenGL 1.4 connectivity vertex transform & lighting primitive assembly rasterization texture fog, texturing framebuffer blending, depth, stencil OpenGL 2.1 connectivity vertex shader primitive assembly rasterization VBO texture framebuffer fragment shader blending, depth, stencil 6

7 Shader processing Parallel processing vertices: properties vertex scheduler vertex processors vertices: positions, properties rasterizer fragments: positions, properties fragment processors framebuffer fragments: colors 7

8 Vertex shader vertices: properties vertex processors vertices: positions, properties Transform Animation Per-vertex lighting Displacement Mostly: Parameter setup for fragments Can not modify topology No access to other vertices Fragment shader fragments: positions, properties fragment processors fragments: colors Per-pixel lighting Texturing Compositing Filtering Fog Can not read or write pixels No access to other fragments 8

9 Simple example Per-pixel lighting 9

10 Vertex shader color = gl_color.rgb; normal = normalize(gl_normalmatrix * gl_normal); pos = vec3(gl_modelviewmatrix * gl_vertex); gl_position = gl_modelviewprojectionmatrix * gl_vertex; Vertex shader color = gl_color.rgb; normal = normalize(gl_normalmatrix * gl_normal); pos = vec3(gl_modelviewmatrix * gl_vertex); uniform (prog. to vertex, per primitive) attribute (prog. to vertex, per vertex) varying (vertex to fragment) gl_position = gl_modelviewprojectionmatrix * gl_vertex; 10

11 Vertex shader color = gl_color.rgb; normal = normalize(gl_normalmatrix * gl_normal); pos = vec3(gl_modelviewmatrix * gl_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) gl_position = gl_modelviewprojectionmatrix * gl_vertex; Vertex shader color = gl_color.rgb; normal = normalize(gl_normalmatrix * gl_normal); pos = vec3(gl_modelviewmatrix * gl_vertex); gl_position = gl_modelviewprojectionmatrix * gl_vertex; 11

12 Vertex shader vertex shader built-in attributes writing to gl_position is mandatory color = gl_color.rgb; normal = normalize(gl_normalmatrix * gl_normal); pos = vec3(gl_modelviewmatrix * gl_vertex); gl_position = gl_modelviewprojectionmatrix * gl_vertex; Vertex shader built-in uniforms color = gl_color.rgb; normal = normalize(gl_normalmatrix * gl_normal); pos = vec3(gl_modelviewmatrix * gl_vertex); gl_position = gl_modelviewprojectionmatrix * gl_vertex; 12

13 Fragment shader uniform float shininess; 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); Fragment shader 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; gl_fragcolor = vec4(color * diff + spec, 1); 13

14 Fragment shader 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); 14