Alexander Romanov
d969192fbe
The patch contains an implementation of the wide lines and the line stipple that is necessary for OpenGL upgrade. For the implementation I have chosen the geometry shader because it required minimum changes for the wrapper calls and such implementation is the best for the "basic shader" architecture. There are few shortcomings that can be corrected in future. They all are related to the fact that the lines in one strip are not connected with each other. So the stipple pattern is not continuous on the common vertex of two lines. There is also no continuity of form (each line is an independent rectangular). But the advantage is that even outdated glBegin, glVertex work! Though with the above restrictions. Continuity of form and stipple can be implemented with additional attributes, and it will require more changes in calls. At the moment, the patch replaces calls for some "gestures". It works satisfactorily for "cross" or "rectangular" and not so good for "lasso" and "circle" due to the above-mentioned shortcomings. Don't forget to set USE_GLSL to true for testing. Alexander Romanov (Blend4Web Team) Reviewers: merwin, brecht Reviewed By: merwin, brecht Subscribers: aligorith, Evgeny_Rodygin, AlexKowel, yurikovelenov Differential Revision: https://developer.blender.org/D1880
101 lines
3.3 KiB
GLSL
101 lines
3.3 KiB
GLSL
/*
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* Used the implementation of wide lines of Timo Suoranta (http://neure.dy.fi/wideline.html)
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*/
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#define PASSTHROUGH 0
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layout(lines) in;
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#if defined(DRAW_LINE)
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#if PASSTHROUGH
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layout(line_strip, max_vertices = 10) out;
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#else
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layout(triangle_strip, max_vertices = 6) out;
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#endif
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varying out float t;
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varying in vec4 varying_vertex_color_line[];
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varying out vec4 varying_vertex_color;
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uniform ivec4 viewport;
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uniform float line_width;
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uniform int stipple_factor;
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void main(void)
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{
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vec2 window_size = viewport.zw;
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vec4 start = gl_in[0].gl_Position;
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vec4 end = gl_in[1].gl_Position;
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#if PASSTHROUGH
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gl_Position = start; EmitVertex();
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gl_Position = end; EmitVertex();
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EndPrimitive();
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return;
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#endif
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/* t = 0 t = ~(len(end - start) + 2*line_width)
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* A-------------------------------------B
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* | | | |
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* | side | |
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* | | | |
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* |--axis--*start--------------*end-----|
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* | | | |
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* | | | |
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* | | | |
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* D-------------------------------------C
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*/
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/* Clip the line before homogenization.
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* Compute line start and end distances to nearplane in clipspace
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* Distances are t0 = dot(start, plane) and t1 = dot(end, plane)
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*/
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float t0 = start.z + start.w;
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float t1 = end.z + end.w;
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if(t0 < 0.0) {
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if(t1 < 0.0) {
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return;
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}
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start = mix(start, end, (0 - t0) / (t1 - t0));
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}
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if(t1 < 0.0) {
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end = mix(start, end, (0 - t0) / (t1 - t0));
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}
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/* Compute line axis and side vector in screen space */
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vec2 startInNDC = start.xy / start.w; /* clip to NDC: homogenize and drop z */
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vec2 endInNDC = end.xy / end.w;
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vec2 lineInNDC = endInNDC - startInNDC;
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vec2 lineInScreen = lineInNDC * window_size; /* ndc to screen (direction vector) */
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vec2 axisInScreen = normalize(lineInScreen);
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vec2 sideInScreen = vec2(-axisInScreen.y, axisInScreen.x); /* rotate */
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vec2 axisInNDC = axisInScreen / window_size; /* screen to NDC */
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vec2 sideInNDC = sideInScreen / window_size;
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vec4 axis = vec4(axisInNDC, 0.0, 0.0) * line_width; /* NDC to clip (delta vector) */
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vec4 side = vec4(sideInNDC, 0.0, 0.0) * line_width;
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vec4 A = (start + (side - axis) * start.w);
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vec4 B = (end + (side + axis) * end.w);
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vec4 C = (end - (side - axis) * end.w);
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vec4 D = (start - (side + axis) * start.w);
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/* There is no relation between lines yet */
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/* TODO Pass here t0 to make continuous pattern. */
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t0 = 0;
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t1 = (length(lineInScreen) + 2*line_width)/ (2*line_width * stipple_factor);
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gl_Position = A; t = t0; varying_vertex_color = varying_vertex_color_line[0]; EmitVertex();
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gl_Position = D; t = t0; varying_vertex_color = varying_vertex_color_line[0]; EmitVertex();
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gl_Position = B; t = t1; varying_vertex_color = varying_vertex_color_line[1]; EmitVertex();
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gl_Position = C; t = t1; varying_vertex_color = varying_vertex_color_line[1]; EmitVertex();
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EndPrimitive();
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}
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#else
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void main(void)
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{
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}
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#endif
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