Rework line shaders for WGLMakie compatability (#3558)

* prototyping * fix joint with non-uniform linewidths * fix transform * add patterns * fix pattern sampling * fix truncated join cutoff + some cleanup * improve pattern overwrite threshhold * reorganize code * cleanup * add function for line vec -> line normal * don't try to cleanup joints if linewidth difference is critical * rename some variables * cleanup comments, restructure linewidth sdf generation * minor cleanup + notes * fix orientation problems with truncated joints * minor performance tweaks + cleanup * handle line joints in fragment shader & ditch variable linewidths * improve truncation overlap/gap * improve pattern adjustments for truncated joints * cleanup * reorganize code to reduce memory usage * mostly fix gap in sharp joints * explain pattern overwrite a bit more * use new fragment shader for linesegments * disable debug rendering * fix incorrect line placement * adjust line segments to pattern * use const over define & fix dots * tweak debug rendering * make truncation overlap a bit nicer * minor cleanup * fix linestyle in linesegments * skip rendering at 0 linewidth * add slight bias to avoid missing pixels * differentiate different segments in debug render * make color interpolation continuous at joint * fix dense line color artifacts * remove unused * allocate space for joints * use sdf for AA + debug render * add miter joints * handle colors * some cleanup + linesegments prep * fix some errors [skip ci] * add patterns * clean up linesegments * add normal rendering mode * minor cleanup * experiment with geometry adjustments * use rounding to solve joint over/underdraw * WebGL doesn't like scaling * smooth out inner edge of truncated join * remove derivative to reduce float accuracy issues * improve thin lines * fix lastlen error * match buffer sizes to number of drawn segments * avoid dissipation of lines at high point densities * calculate uv from quad_sdf1 * reduce number of interleaved buffers * fix disappearing grid lines * fix missing preprocessors * fix pattern artifacts in dense line sections * cleanup some variables * allow patterns to adjust to linewidth * fix AA at line end * fix nan handling * discard fully transparent pixels * fix patterns with nan, reset pattern on nan * fix size issues * extrude lines slightly to cleanly close them * fix pixel skipping? * cleanup patterns * remove linewidth from pattern based line adjustments * consider AA in shape factor * reset shape_factor if pattern changes segment shape * minor cleanup * apply changes to WGLMakie + cleanup * cleanup pattern overwrite * use the same AA_RADIUS in fragment shader * fix linelen transform * disable debug * fix line start/end AA * fix px_per_unit? * fix px_per_unit? * reduce line start/end extrusion * simplify extrusion and shape_factor * summarize breaking changes * move miter joint test * update docstring * minor cleanup * enable more tests * move gappy & friends to Makie * note change to linestyle scaling * cleanup * fix line start/end AA * remove global var * disable GeoMakie tests for now * improve transparency for WGLMakie * fix problems with 180° change in line direction * fix directionality * interpolate colormap in fragment shader * remove util.vert from line/segments --------- Co-authored-by: SimonDanisch <[email protected]>
MakieOrg · Feb 27, 2024 · 3f885c3 · 3f885c3
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,16 @@
 
 ## [Unreleased]
 
+- **Breaking** Reworked line shaders in GLMakie and WGLMakie [#3558](https://github.com/MakieOrg/Makie.jl/pull/3558)
+  - GLMakie: Removed support for per point linewidths
+  - GLMakie: Adjusted dots (e.g. with `linestyle = :dot`) to bend across a joint
+  - GLMakie: Adjusted linestyles to scale with linewidth dynamically so that dots remain dots with changing linewidth
+  - GLMakie: Cleaned up anti-aliasing for truncated joints
+  - WGLMakie: Added support for linestyles
+  - WGLMakie: Added line joints
+  - WGLMakie: Added native anti-aliasing which generally improves quality but introduces outline artifacts in some cases (same as GLMakie)
+  - Both: Adjusted handling of thin lines which may result in different color intensities
+
 ## [0.20.8] - 2024-02-22
 
 - Fixed excessive use of space with HTML image outputs [#3642](https://github.com/MakieOrg/Makie.jl/pull/3642).

diff --git a/CairoMakie/test/runtests.jl b/CairoMakie/test/runtests.jl
@@ -184,7 +184,8 @@ excludes = Set([
     "scatter with glow",
     "scatter with stroke",
     "heatmaps & surface",
-    "Textured meshscatter" # not yet implemented
+    "Textured meshscatter", # not yet implemented
+    "Miter Joints for line rendering", # CairoMakie does not show overlap here and extrudes lines a little more
 ])
 
 functions = [:volume, :volume!, :uv_mesh]

diff --git a/GLMakie/assets/shader/line_segment.geom b/GLMakie/assets/shader/line_segment.geom
@@ -1,8 +1,6 @@
 {{GLSL_VERSION}}
 {{GLSL_EXTENSIONS}}
 
-{{define_fast_path}}
-
 struct Nothing{ //Nothing type, to encode if some variable doesn't contain any data
     bool _; //empty structs are not allowed
 };
@@ -14,37 +12,36 @@ uniform vec2 resolution;
 uniform float pattern_length;
 {{pattern_type}} pattern;
 
-in vec4 g_color[];
+in {{stripped_color_type}} g_color[];
 in uvec2 g_id[];
 in float g_thickness[];
 
-out float f_thickness;
-out vec4 f_color;
-out vec2 f_uv;
-flat out uvec2 f_id;
-flat out vec2 f_uv_minmax;
-
-#define AA_THICKNESS 4.0
-
-// Get pattern values
-float fetch(Nothing _, float u){return 10000000.0;}
-float fetch(sampler1D pattern, float u){return texture(pattern, u).x;}
+out float f_quad_sdf0;
+out vec3 f_quad_sdf1;
+out float f_quad_sdf2;
+out vec2 f_truncation;
+out float f_linestart;
+out float f_linelength;
 
-vec3 screen_space(vec4 vertex)
-{
-    return vec3(vertex.xy * resolution, vertex.z) / vertex.w;
+flat out float f_linewidth;
+flat out vec4 f_pattern_overwrite;
+flat out uvec2 f_id;
+flat out vec2 f_extrusion;
+flat out vec2 f_discard_limit;
+flat out {{stripped_color_type}} f_color1;
+flat out {{stripped_color_type}} f_color2;
+flat out float f_alpha_weight;
+flat out float f_cumulative_length;
+
+const float AA_RADIUS = 0.8;
+const float AA_THICKNESS = 2.0 * AA_RADIUS;
+
+vec3 screen_space(vec4 vertex) {
+    return vec3((0.5 * vertex.xy / vertex.w + 0.5) * resolution, vertex.z / vertex.w);
 }
 
-void emit_vertex(vec3 position, vec2 uv, int index)
-{
-    vec4 inpos = gl_in[index].gl_Position;
-    f_uv = uv;
-    f_color = g_color[index];
-    gl_Position = vec4((position.xy / resolution), position.z, 1.0);
-    f_id = g_id[index];
-    f_thickness = g_thickness[index];
-    EmitVertex();
-}
+vec2 normal_vector(in vec2 v) { return vec2(-v.y, v.x); }
+vec2 normal_vector(in vec3 v) { return vec2(-v.y, v.x); }
 
 out vec3 o_view_pos;
 out vec3 o_view_normal;
@@ -54,54 +51,71 @@ void main(void)
     o_view_pos = vec3(0);
     o_view_normal = vec3(0);
 
-    // get the four vertices passed to the shader:
-    vec3 p0 = screen_space(gl_in[0].gl_Position); // start of previous segment
-    vec3 p1 = screen_space(gl_in[1].gl_Position); // end of previous segment, start of current segment
-
-    float thickness_aa0 = g_thickness[0] + AA_THICKNESS;
-    float thickness_aa1 = g_thickness[1] + AA_THICKNESS;
-    // determine the direction of each of the 3 segments (previous, current, next)
-    vec3 vun0 = p1 - p0;
-    vec3 v0 = vun0 / length(vun0.xy);
-    // determine the normal of each of the 3 segments (previous, current, next)
-    vec3 n0 = vec3(-v0.y, v0.x, 0);
-    float l = length(p1 - p0);
-    float px2u = 0.5 / pattern_length;
-    float u = l * px2u;
-
-    vec3 AA_offset = AA_THICKNESS * v0;
-    float AA = AA_THICKNESS * px2u;
-
-    /*                  0              v0              l
-                        |             -->              |
-     -thickness_aa0 - .----------------------------------. - -thickness_aa1
-    -g_thickness[0] - | .------------------------------. | - -g_thickness[1]
-                      | |                              | |
-                n0 ↑  | |                              | |
-                      | |                              | |
-    +g_thickness[0] - | '------------------------------' | - +g_thickness[1]
-     +thickness_aa0 - '----------------------------------' - +thickness_aa1
-                      |                                  |
-                -AA_THICKNESS                    l + AA_THICKNESS
-    */
-
-    #ifdef FAST_PATH
-        // For solid lines the uv cordinates are used as a signed distance field.
-        // We keep the values positive to draw a solid line and add limits to
-        // f_uv_minmax to add anti-aliasing at the start and end of the line
-        f_uv_minmax = vec2(u, 2*u);
-        emit_vertex(p0 + thickness_aa0 * n0 - AA_offset, vec2(  u - AA, -thickness_aa0), 0);
-        emit_vertex(p0 - thickness_aa0 * n0 - AA_offset, vec2(  u - AA,  thickness_aa0), 0);
-        emit_vertex(p1 + thickness_aa1 * n0 + AA_offset, vec2(2*u + AA, -thickness_aa1), 1);
-        emit_vertex(p1 - thickness_aa1 * n0 + AA_offset, vec2(2*u + AA,  thickness_aa1), 1);
-    #else
-        // For patterned lines AA is mostly done by the pattern sampling. We
-        // still set f_uv_minmax here to ensure that cut off patterns als have
-        // anti-aliasing at the start/end of this segment
-        f_uv_minmax = vec2(0, u);
-        emit_vertex(p0 + thickness_aa0 * n0 - AA_offset, vec2(  - AA, -thickness_aa0), 0);
-        emit_vertex(p0 - thickness_aa0 * n0 - AA_offset, vec2(  - AA,  thickness_aa0), 0);
-        emit_vertex(p1 + thickness_aa1 * n0 + AA_offset, vec2(u + AA, -thickness_aa1), 1);
-        emit_vertex(p1 - thickness_aa1 * n0 + AA_offset, vec2(u + AA,  thickness_aa1), 1);
-    #endif
+    // we generate very thin lines for linewidth 0, so we manually skip them:
+    if (g_thickness[0] == 0.0 && g_thickness[1] == 0.0) {
+        return;
+    }
+
+    // get start and end point of line segment
+    vec3 p1 = screen_space(gl_in[0].gl_Position);
+    vec3 p2 = screen_space(gl_in[1].gl_Position);
+
+    // get vector in line direction and vector in linewidth direction
+    vec3 v1 = (p2 - p1);
+    float segment_length = length(p2.xy - p1.xy);
+    v1 /= segment_length;
+    vec2 n1 = normal_vector(v1);
+
+    // Set invalid / ignored outputs
+    f_quad_sdf0 = 10.0;             // no joint to previous segment
+    f_quad_sdf2 = 10.0;             // not joint to next segment
+    f_truncation = vec2(-10.0);     // no truncated joint
+    f_pattern_overwrite = vec4(-1e12, 1.0, 1e12, 1.0); // no joints to overwrite
+    f_extrusion = vec2(0.5);        // no joints needing extrusion
+    f_discard_limit = vec2(10.0);   // no joints needing discards
+
+    // constants
+    f_color1 = g_color[0];
+    f_color2 = g_color[1];
+    f_alpha_weight = min(1.0, g_thickness[0] / AA_RADIUS);
+    f_linestart = 0;                // no corners so no joint extrusion to consider
+    f_linelength = segment_length;  // and also no changes in line length
+    f_cumulative_length = 0.0;      // resets for each new segment
+
+    // Generate vertices
+
+    for (int x = 0; x < 2; x++) {
+        // Get offset in line direction
+        float v_offset = (2 * x - 1) * AA_THICKNESS;
+        // pass on linewidth and id (picking) for the current line vertex
+        float halfwidth = 0.5 * max(AA_RADIUS, g_thickness[x]);
+        // TODO: if we just make this a varying output we probably get var linewidths here
+        f_linewidth = halfwidth;
+        f_id = g_id[x];
+
+        for (int y = 0; y < 2; y++) {
+            // Get offset in y direction & compute vertex position
+            float n_offset = (2 * y - 1) * (halfwidth + AA_THICKNESS);
+            vec3 position = vec3[2](p1, p2)[x] + v_offset * v1 + n_offset * vec3(n1, 0);
+            gl_Position = vec4(2.0 * position.xy / resolution - 1.0, position.z, 1.0);
+
+            // Generate SDF's
+
+            // distance from quad vertex to line control points
+            vec2 VP1 = position.xy - p1.xy;
+            vec2 VP2 = position.xy - p2.xy;
+
+            // sdf of this segment
+            f_quad_sdf1.x = dot(VP1, -v1.xy);
+            f_quad_sdf1.y = dot(VP2,  v1.xy);
+            f_quad_sdf1.z = n_offset;
+
+            // finalize vertex
+            EmitVertex();
+        }
+    }
+
+    EndPrimitive();
+
+    return;
 }
diff --git a/GLMakie/assets/shader/line_segment.vert b/GLMakie/assets/shader/line_segment.vert
@@ -8,41 +8,24 @@ struct Nothing{ //Nothing type, to encode if some variable doesn't contain any d
 in float lastlen;
 {{vertex_type}} vertex;
 {{thickness_type}} thickness;
-
 {{color_type}} color;
-{{color_map_type}} color_map;
-{{color_norm_type}} color_norm;
 
 uniform mat4 projectionview, model;
 uniform uint objectid;
 uniform float depth_shift;
 uniform float px_per_unit;
 
 out uvec2 g_id;
-out vec4 g_color;
+out {{stripped_color_type}} g_color;
 out float g_thickness;
 
-vec4 getindex(sampler2D tex, int index);
-vec4 getindex(sampler1D tex, int index);
-vec4 color_lookup(float intensity, sampler1D color_ramp, vec2 norm);
-
 vec4 to_vec4(vec3 v){return vec4(v, 1);}
 vec4 to_vec4(vec2 v){return vec4(v, 0, 1);}
 
-vec4 to_color(vec4 v, Nothing color_map, Nothing color_norm, int index){return v;}
-vec4 to_color(vec3 v, Nothing color_map, Nothing color_norm, int index){return vec4(v, 1);}
-vec4 to_color(sampler1D tex, Nothing color_map, Nothing color_norm, int index){return getindex(tex, index);}
-vec4 to_color(sampler2D tex, Nothing color_map, Nothing color_norm, int index){return getindex(tex, index);}
-vec4 to_color(float color, sampler1D color_map, vec2 color_norm, int index){
-    return color_lookup(color, color_map, color_norm);
-}
-
-
 void main()
 {
-    int index = gl_VertexID;
-    g_id = uvec2(objectid, index+1);
-    g_color = to_color(color, color_map, color_norm, index);
+    g_id = uvec2(objectid, gl_VertexID + 1);
+    g_color = color;
     g_thickness = px_per_unit * thickness;
     gl_Position = projectionview * model * to_vec4(vertex);
     gl_Position.z += gl_Position.w * depth_shift;