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49 lines
1.4 KiB
GLSL
49 lines
1.4 KiB
GLSL
#version 400 core
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// Based on http://prideout.net/blog/?p=64
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layout(points) in;
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layout(triangle_strip, max_vertices = 24) out;
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uniform mat4 modelViewProjection;
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in vec4 vPosition[1];
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vec4 objCube[8]; // Object space coordinate of cube corner
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vec4 ndcCube[8]; // Normalized device coordinate of cube corner
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ivec4 faces[6]; // Vertex indices of the cube faces
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void emit_vert(int vert) {
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gl_Position = ndcCube[vert];
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EmitVertex();
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}
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void emit_face(int face) {
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emit_vert(faces[face][1]); emit_vert(faces[face][0]);
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emit_vert(faces[face][3]); emit_vert(faces[face][2]);
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EndPrimitive();
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}
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void main() {
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faces[0] = ivec4(0,1,3,2); faces[1] = ivec4(5,4,6,7);
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faces[2] = ivec4(4,5,0,1); faces[3] = ivec4(3,2,7,6);
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faces[4] = ivec4(0,3,4,7); faces[5] = ivec4(2,1,6,5);
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float size = 0.5;
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vec4 P = vPosition[0];
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vec4 I = vec4(size, 0, 0, 0);
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vec4 J = vec4(0, size, 0, 0);
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vec4 K = vec4(0, 0, size, 0);
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objCube[0] = P+K+I+J; objCube[1] = P+K+I-J;
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objCube[2] = P+K-I-J; objCube[3] = P+K-I+J;
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objCube[4] = P-K+I+J; objCube[5] = P-K+I-J;
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objCube[6] = P-K-I-J; objCube[7] = P-K-I+J;
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// Transform the corners of the box:
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for (int vert = 0; vert < 8; vert++)
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ndcCube[vert] = modelViewProjection * objCube[vert];
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// Emit the six faces:
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for (int face = 0; face < 6; face++)
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emit_face(face);
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}
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