Mike Erwin
5b26c36008
As seen at #bcon16. These were produced quickly and probably need further work. SIMPLE variant draws triangle mesh edges. Based on this research: http://www2.imm.dtu.dk/pubdb/views/edoc_download.php/4884/pdf/imm4884.pdf http://developer.download.nvidia.com/SDK/10/direct3d/Source/SolidWireframe/Doc/SolidWireframe.pdf Non-SIMPLE variant can adjust thickness per edge. This can be used to draw only some edges, or accentuate some edges. Given the right inputs this is a general n-gon perimeter shader. Part of T49165
68 lines
1.4 KiB
GLSL
68 lines
1.4 KiB
GLSL
layout(triangles) in;
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layout(triangle_strip, max_vertices=3) out;
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uniform float outlineWidth = 1.0;
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uniform vec2 viewportSize;
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in vec4 pos_xformed[];
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in float widthModulator[];
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noperspective out vec3 distanceToOutline;
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// project to screen space
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vec2 proj(int axis) {
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vec4 pos = pos_xformed[axis];
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return (0.5 * (pos.xy / pos.w) + 0.5) * viewportSize;
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}
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float dist(vec2 pos[3], int v) {
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// current vertex position
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vec2 vpos = pos[v];
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// endpoints of opposite edge
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vec2 e1 = pos[(v + 1) % 3];
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vec2 e2 = pos[(v + 2) % 3];
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float abs_det = length(cross(vec3(vpos - e1, 0), vec3(vpos - e2, 0))); // could simplify
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return abs_det / distance(e2, e1);
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}
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vec3 distance[3];
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void clearEdge(int v) {
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float distant = 10 * outlineWidth;
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for (int i = 0; i < 3; ++i)
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distance[i][v] += distant;
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}
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void modulateEdge(int v) {
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float offset = min(widthModulator[v],1) * outlineWidth;
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for (int i = 0; i < 3; ++i)
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distance[i][v] -= offset;
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}
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void main() {
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vec2 pos[3] = vec2[3](proj(0), proj(1), proj(2));
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for (int v = 0; v < 3; ++v)
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distance[v] = vec3(0);
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for (int v = 0; v < 3; ++v) {
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if (widthModulator[v] > 0) {
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distance[v][v] = dist(pos, v);
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modulateEdge(v);
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}
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}
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for (int v = 0; v < 3; ++v)
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if (widthModulator[v] <= 0)
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clearEdge(v);
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for (int v = 0; v < 3; ++v) {
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gl_Position = pos_xformed[v];
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distanceToOutline = distance[v];
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EmitVertex();
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}
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EndPrimitive();
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}
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