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# What it covers:
# * tessellation of quads
# * different number of input (pre-TCS) and output (post-TCS) control points
# * all inputs are read in each shader
# * gl_PatchVerticesIn in TCS and TES
#
# How it works:
# * There is a patch with 4 control points on the input (quad).
# * The TCS subdivides the patch into 9 control points (4 tiles in a 2x2 pattern).
# * A color is assigned to each tile, which is held in the upper-left corner
# of the tile.
# * The 2x2 pattern is still a single quad from the tessellator point of view.
# * The tessellator should create 21*21 quads (21*21*2 triangles).
# * The quad should be tessellated such that you can clearly see 4 tiles that
# have different colors. The triangles in the middle should smoothly blend
# colors from both tiles (caused by interpolation of varyings).
#
[require]
GLSL >= 1.50
GL_ARB_tessellation_shader
[vertex shader]
#version 150
in vec4 vertex;
void main()
{
gl_Position = vec4(vertex.xy, 0, 1);
}
[tessellation control shader]
#version 150
#extension GL_ARB_tessellation_shader : require
layout(vertices = 9) out;
out vec4 color[];
out vec4 pos[];
void main()
{
float t = 21;
gl_TessLevelInner[0] = t;
gl_TessLevelInner[1] = t;
gl_TessLevelOuter[0] = t;
gl_TessLevelOuter[1] = t;
gl_TessLevelOuter[2] = t;
gl_TessLevelOuter[3] = t;
float x = float(gl_InvocationID % 3) / 2;
float y = float(gl_InvocationID / 3) / 2;
vec4 x1 = mix(gl_in[0].gl_Position, gl_in[1].gl_Position, x);
vec4 x2 = mix(gl_in[2].gl_Position, gl_in[3].gl_Position, x);
pos[gl_InvocationID] = mix(x1, x2, y);
color[gl_InvocationID] = gl_PatchVerticesIn == 4 ? vec4(x, y, 0, 1) : vec4(0);
}
[tessellation evaluation shader]
#version 150
#extension GL_ARB_tessellation_shader : require
layout(quads, equal_spacing) in;
in vec4 pos[];
in vec4 color[];
out vec4 fs_color;
void main()
{
float x = gl_TessCoord.x;
float y = gl_TessCoord.y;
vec4 vx[3], cx[3], v, c;
for (int i = 0; i < 3; i++) {
if (x <= 0.5) {
vx[i] = mix(pos[i*3], pos[i*3+1], x*2);
cx[i] = color[i*3];
} else {
vx[i] = mix(pos[i*3+1], pos[i*3+2], (x-0.5)*2);
cx[i] = color[i*3+1];
}
}
if (y <= 0.5) {
v = mix(vx[0], vx[1], y*2);
c = cx[0];
} else {
v = mix(vx[1], vx[2], (y-0.5)*2);
c = cx[1];
}
gl_Position = v;
fs_color = gl_PatchVerticesIn == 9 ? c : vec4(0);
}
[fragment shader]
#version 150
in vec4 fs_color;
void main()
{
gl_FragColor = fs_color;
}
[vertex data]
vertex/float/2
-1.0 -1.0
1.0 -1.0
-1.0 1.0
1.0 1.0
[test]
clear color 0.1 0.1 0.1 0.1
clear
patch parameter vertices 4
draw arrays GL_PATCHES 0 4
relative probe rect rgb (0.0 , 0.0 , 0.476, 0.476) (0.0, 0.0, 0.0)
relative probe rect rgb (0.524, 0.0 , 0.476, 0.476) (0.5, 0.0, 0.0)
relative probe rect rgb (0.0 , 0.524, 0.476, 0.476) (0.0, 0.5, 0.0)
relative probe rect rgb (0.524, 0.524, 0.476, 0.476) (0.5, 0.5, 0.0)
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