From 9a5ef19d5971488de18539eaf68e35bf590a4c5e Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Fri, 28 Aug 2020 07:16:51 -0400
Subject: render: Add vector path rendering module.

---
 data/shaders/path-frag.glsl | 93 +++++++++++++++++++++++++++++++++++++++++++++
 data/shaders/path-vert.glsl | 44 +++++++++++++++++++++
 2 files changed, 137 insertions(+)
 create mode 100644 data/shaders/path-frag.glsl
 create mode 100644 data/shaders/path-vert.glsl

(limited to 'data/shaders')

diff --git a/data/shaders/path-frag.glsl b/data/shaders/path-frag.glsl
new file mode 100644
index 0000000..a38f1d0
--- /dev/null
+++ b/data/shaders/path-frag.glsl
@@ -0,0 +1,93 @@
+// -*- mode: c -*-
+
+#ifdef GLSL330
+out vec4 fragColor;
+#endif
+
+#ifdef GLSL120
+attribute vec2 fragTex;
+attribute float fragStrokeLength;
+#else
+in vec2 fragTex;
+in float fragStrokeLength;
+#endif
+
+uniform int mode;
+uniform vec4 color;
+uniform float feather;
+uniform int strokeClosed;
+uniform float strokeWidth;
+uniform int strokeCap;
+uniform int strokeMiterStyle;
+uniform float strokeMiterLimit;
+
+float infinity = 1.0 / 0.0;
+
+void main(void) {
+  if (color.a <= 0.0) {
+    discard;
+  }
+
+  // fill mode
+  if(mode == 0) {
+#ifdef GLSL330
+    fragColor = color;
+#else
+    gl_FragColor = color;
+#endif
+  } else if(mode == 1) { // stroke mode
+    float hw = strokeWidth / 2.0;
+    float u = fragTex.x;
+    float v = fragTex.y;
+    float dx;
+    float dy;
+    float d;
+
+    // Stroke caps.
+    if (u < 0 || u > fragStrokeLength) {
+      if (u < 0) {
+        dx = abs(u);
+      } else {
+        dx = u - fragStrokeLength;
+      }
+      dy = abs(v);
+
+      if (strokeCap == 0) { // none
+        d = infinity;
+      } else if (strokeCap == 1) { // butt
+        d = max(dx + hw - 2 * feather, dy);
+      } else if (strokeCap == 2) { // square
+        d = max(dx, dy);
+      } else if (strokeCap == 3) { // round
+        d = sqrt(dx * dx + dy * dy);
+      } else if (strokeCap == 4) { // triangle out
+        d = dx + dy;
+      } else if (strokeCap == 5) { // triangle in
+        d = max(dy, hw - feather + dx - dy);
+      }
+    // Stroke inner/join
+    } else {
+      d = abs(v);
+    }
+
+    if(d <= hw) {
+#ifdef GLSL330
+      fragColor = color;
+#else
+      gl_FragColor = color;
+#endif
+    } else {
+      vec4 c = vec4(color.rgb, color.a * (1.0 - ((d - hw) / feather)));
+
+      if (c.a <= 0.0) {
+        discard;
+      }
+
+#ifdef GLSL330
+      fragColor = c;
+#else
+      gl_FragColor = c;
+#endif
+    }
+  }
+}
diff --git a/data/shaders/path-vert.glsl b/data/shaders/path-vert.glsl
new file mode 100644
index 0000000..38fa5d2
--- /dev/null
+++ b/data/shaders/path-vert.glsl
@@ -0,0 +1,44 @@
+// -*- mode: c -*-
+
+#ifdef GLSL330
+layout (location = 0) in vec2 position;
+layout (location = 1) in vec2 tex;
+layout (location = 2) in float strokeLength;
+#elif defined(GLSL130)
+in vec2 position;
+in vec2 tex;
+in float strokeLength;
+#elif defined(GLSL120)
+attribute vec2 position;
+attribute vec2 tex;
+attribute float strokeLength;
+#endif
+
+#ifdef GLSL120
+varying vec2 fragTex;
+varying float fragStrokeLength;
+#else
+out vec2 fragTex;
+out float fragStrokeLength;
+#endif
+
+uniform mat4 mvp;
+uniform vec4 color;
+uniform int mode;
+uniform int strokeClosed;
+
+void main(void) {
+    // Short-circuit because the fragments will just be discarded anyway.
+    if (color.a <= 0.0) {
+      gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
+      return;
+    }
+
+    // Stroke specific setup.
+    if (mode == 1) {
+      fragStrokeLength = strokeLength;
+    }
+
+    fragTex = tex;
+    gl_Position = mvp * vec4(position.xy, 0.0, 1.0);
+}
-- 
cgit v1.2.3