[openrndr-demos] Add DemoTessShader04

openrndr-demos/src/demo/resources/shaders/ts-04.tese

@@ -0,0 +1,48 @@
+#version 430 core
+
+vec3 bezier2(vec3 a, vec3 b, float t) {
+    return mix(a, b, t);
+}
+vec3 bezier3(vec3 a, vec3 b, vec3 c, float t) {
+    return mix(bezier2(a, b, t), bezier2(b, c, t), t);
+}
+vec3 bezier4(vec3 a, vec3 b, vec3 c, vec3 d, float t) {
+    return mix(bezier3(a, b, c, t), bezier3(b, c, d, t), t);
+}
+
+struct Vertex {
+    vec3 va_position;
+    vec3 va_normal;
+    vec4 v_addedProperty;
+};
+
+layout(isolines) in;
+in vec3 cva_position[];
+
+out vec3 derivative;
+out vec3 position;
+
+uniform int resolution;
+
+uniform mat4 proj;
+uniform mat4 view;
+uniform mat4 model;
+
+void main() {
+    float t = gl_TessCoord.x;
+    vec3 ePos = bezier4(
+    cva_position[0],
+    cva_position[1],
+    cva_position[2],
+    cva_position[3],
+    t);
+
+    // calculate derivative using Hodograph
+    derivative = bezier3(cva_position[1] - cva_position[0], cva_position[2]-cva_position[1], cva_position[3]-cva_position[2], t);
+
+    // output model space positions
+    position = ePos;
+
+    float r = resolution + 1.0;
+    //gl_Position = proj * view * model * vec4(ePos, 1);
+}