texture content setting refactor, 3d shader example

demo/3dt.fs

@@ -0,0 +1,44 @@
+#define STEPSIZE .1
+#define DENSCALE .1
+
+void main() {
+  // Compute the pixel's position in view space.
+  vec2 fragCoord = gl_FragCoord.xy / resolution.xy;
+  vec3 viewPos = vec3((fragCoord * 2.0 - 1.0), 0.5);
+  viewPos.y *= -1.0; // Flip Y axis to match WebGL convention.
+
+  vec3 camPos = vec3(.5 + m.x * .5, .5 + m.y * .5, -.25);
+  vec3 camDir = vec3(1., 1., 1.);
+
+  // Convert the pixel's position to world space.
+  vec3 worldPos = camPos + viewPos * length(camDir);
+
+  // Compute the ray direction in world space.
+  vec3 rayDir = normalize(worldPos - camPos);
+
+  // Initialize the color and transparency values.
+  vec4 color = vec4(0.0);
+  float alpha = 0.0;
+
+  // Perform the ray-marching loop.
+  for (float t = 0.0; t < 2.0; t += STEPSIZE) {
+    // Compute the position along the ray.
+    vec3 pos = camPos + rayDir * t;
+
+    // Sample the density at the current position.
+    float density = texture(test3d, pos).x * DENSCALE;
+
+    // Accumulate the color and transparency values.
+    vec4 sampleColor = vec4(1.0, 0.5, 0.2, 1.0);
+    color += (1.0 - alpha) * sampleColor * density;
+    alpha += (1.0 - alpha) * density;
+
+    // Stop marching if the transparency reaches 1.0.
+    if (alpha >= 1.0) {
+      break;
+    }
+  }
+
+  // Output the final color and transparency.
+  o = vec4(color.rgb, alpha);
+}