lab02-debugging

Yi Liu

Setup

Create a Shadertoy account. Either fork this shadertoy, or create a new shadertoy and copy the code from the Debugging Puzzle.

Shader Link

https://www.shadertoy.com/view/M3fcD2

Bug1: Syntax Error

• Issue: The variable uv2 was declared as vec instead of vec2.
• Fix: Change the type of uv2 to vec2.
• How It Was Found: The Shadertoy editor highlighted this as a syntax error upon running the shader.

Bug2: Incorrect Input to raycast Function

• Issue: The uv variable was incorrectly used when calling the raycast function.
• Fix: Use uv2 instead of uv when calling raycast to ensure proper coordinates are passed.
• How It Was Found: The rendered output was distorted, leading to inspection of how coordinates were handled.

Bug3: Reflection Calculation Error

• Issue: The reflection was not computed correctly due to the misuse of the reflect function.
• Fix: Update the reflect function call to use the correct vector inputs:

dir = reflect(dir, nor);

• How It Was Found: The reflection on objects appeared incorrect, leading a deeper look into the reflection calculation.

Bug4: Scene Aspect Ratio Distortion

• Issue: The rendered scene was stretched along the x-axis, showing ellipsoids instead of spheres.
• Fix: Adjust the scene's aspect ratio to prevent distortion.

uv2.x *= iResolution.x; 
uv2.x /= iResolution.y;

• How It Was Found: Comparing the reference Shadertoy to the current output revealed the ratio issue.

Bug5: Insufficient Iterations in march Function

• Issue: The march function was not iterating through enough steps, causing the scene to render incorrectly.
• Fix: Increase the number of iterations in the march function to allow sufficient steps for ray marching:

for (int i = 0; i < 300; ++i) { ... }

• How It Was Found: Visual artifacts and incomplete rendering prompted the inspection of the march funtion.