From a7328150c12a4ace65f1a462bc70f9c98ce133be Mon Sep 17 00:00:00 2001
From: Chang Liu <48054481+HummaWhite@users.noreply.github.com>
Date: Tue, 26 Sep 2023 10:18:04 -0400
Subject: [PATCH] Update README.md

---
 README.md | 132 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)

diff --git a/README.md b/README.md
index aa0f112..b61dfbe 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,137 @@
 # lab06-debugging
 
+# Members
+- Chang Liu
+
+# Link
+- [https://www.shadertoy.com/view/msKcRR](https://www.shadertoy.com/view/msKcRR)
+
+# Bugs Found
+See comments in code
+```GLSL
+void raycast(vec2 uv, out vec3 dir,
+             out vec3 eye, out vec3 ref) {
+    eye = rotateY(vec3(0.0, 0.0, 15.0), sin(iTime * 0.1) * 3.14159 * 0.5);
+    ref = vec3(0.0, 0.0, 0.0);
+    
+    float len = tan(3.14159 * 0.125) * distance(eye, ref);
+    vec3 H = normalize(cross(vec3(0.0, 1.0, 0.0), ref - eye));
+    vec3 V = normalize(cross(H, eye - ref));
+    V *= len;
+
+    // ============================== bug2 ===================================
+    // the aspect ratio wasn't correct
+    // iResolution.x / iResolution.x ---> iResolution.x / iResolution.y
+
+    H *= len * iResolution.x / iResolution.y;
+    vec3 p = ref + uv.x * H + uv.y * V;
+    dir = normalize(p - eye);
+}
+
+void march(vec3 origin, vec3 dir, out float t, out int hitObj) {
+    t = 0.001;
+
+    // ============================== bug5 ===================================
+    // march more times so rays won't be terminated early
+
+    for(int i = 0; i < 256; ++i) { 
+        vec3 pos = origin + t * dir;
+    	float m;
+        sceneMap3D(pos, m, hitObj);
+        if(m < 0.01) {
+            return;
+        }
+        t += m;
+    }
+    t = -1.0;
+    hitObj = -1;
+}
+
+
+vec3 computeMaterial(int hitObj, vec3 p, vec3 d, vec3 n) {
+    switch(hitObj) {
+        case 0:
+        // Center sphere
+        return vec3(1.0, 0.67, 0.67);
+        break;
+        case 1:
+        // Back sphere
+        return vec3(0.67, 1.0, 0.67);
+        break;
+        case 2:
+        // Front sphere
+        return vec3(0.67, 0.67, 1.0);
+        break;
+        case 3:
+        // Floor
+        float t = floor(mod((sin(p.x) + sin(p.z)) * 0.5, 2.0));
+        return mix(vec3(0.7, 0.4, 0.2), vec3(1.0), t);
+        break;
+        case -1:
+        // Background
+        break;
+    }
+    return vec3(255.0, 229.0, 119.0) / 255.0;
+}
+
+Intersection sdf3D(vec3 dir, vec3 eye) {
+    float t;
+    int hitObj;
+    march(eye, dir, t, hitObj);
+    
+    if(t == -1.0) {
+        return Intersection(t, skyColor(dir),
+                            vec3(eye + 1000.0 * dir),
+                            -1);
+    }
+
+    vec3 isect = eye + t * dir;
+    vec3 nor = computeNormal(isect);
+    
+    vec3 material = computeMaterial(hitObj, isect, dir, nor);
+    
+    // ============================== bug4 ===================================
+    // it was 'dir = reflect(eye, nor)', which was wrong
+
+    dir = reflect(dir, nor);
+    march(isect + dir * 0.01, dir, t, hitObj);
+    vec3 specReflCol;
+    if(hitObj == -1) {
+        specReflCol = skyColor(dir);
+    }
+    else {
+        vec3 isect2 = isect + t * dir;
+        nor = computeNormal(isect2);
+        specReflCol = computeMaterial(hitObj, isect2, dir, nor);
+    }
+    float fresnel = 1.0 - max(0.0, dot(normalize(eye - isect), nor));
+    fresnel = 0.25 + 0.75 * fresnel;
+    vec3 sdfColor = mix(material, specReflCol * material, fresnel);
+    
+    return Intersection(t, sdfColor, isect, hitObj);
+}
+
+void mainImage( out vec4 fragColor, in vec2 fragCoord ) {
+    // Normalized pixel coordinates (from 0 to 1)
+    vec2 uv = fragCoord/iResolution.xy;
+    // [-1, 1]
+
+    // ============================== bug4 ===================================
+    // it was 'vec uv = ...', which caused a compilation error
+
+    vec2 uv2 = 2.0 * uv - vec2(1.0);
+    
+    vec3 dir, eye, ref;
+
+    // ============================== bug3 ===================================
+    // uv2 instead of uv should be passed here
+
+    raycast(uv2, dir, eye, ref);
+    fragColor = vec4(sdf3D(dir, eye).color, 1.);
+    
+}
+```
+
 # Setup 
 
 Create a [Shadertoy account](https://www.shadertoy.com/). Either fork this shadertoy, or create a new shadertoy and copy the code from the [Debugging Puzzle](https://www.shadertoy.com/view/flGfRc).