GLSL Learning

GLSL shader example

Ray Marching an SDF Sphere

Trace one ray per pixel, advancing by the distance field. A hit epsilon and maximum distance terminate the loop.

Live example

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What to observe

Ray Marching an SDF Sphere.

Mechanism

Trace one ray per pixel, advancing by the distance field. A hit epsilon and maximum distance terminate the loop.

The controlling code

return length(p)-.75;

Experiment

Change the radius in scene(p)=length(p)-.75 from .75 to .5. The sphere silhouette becomes smaller, while the camera position and perspective stay fixed.

Debugging and cost

The hit test d<.002 and 80-step cap jointly decide when tracing stops. Increase the hit tolerance to .02 to see a less precise surface boundary; a larger tolerance is not the same as increasing the sphere's radius in scene.

Understand the technique

Built-in functions used

abs()floor()fract()min()max()clamp()mix()sin()cos()sqrt()length()dot()normalize()

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