CODEWITHSUNDEEP
openglglslraytracing
Abhishek Bansal
Abhishek Bansal

Reputation: 5335

Doubts in RayTracing with GLSL

I am trying to develop a basic Ray Tracer. So far i have calculated intersection with a plane and blinn-phong shading.i am working on a 500*500 window and my primary ray generation code is as follows

vec3 rayDirection  =   vec3( gl_FragCoord.x-250.0,gl_FragCoord.y-250.0 , 10.0);

Now i doubt that above method is right or wrong. Please give me some insights.

I am also having doubt that do we need to construct geometry in OpenGL code while rayTracing in GLSL. for example if i am trying to raytrace a plane do i need to construct plane in OpenGL code using glVertex2f ?

Upvotes: 1

Views: 2365

Answers (2)

emackey
emackey

Reputation: 12418

It is possible to use Ray Marching to render certain types of complex scenes in a single fragment shader. Here are some examples: (use Chrome or FireFox, requires WebGL)

Gift boxes: http://glsl.heroku.com/e#820.2

Torus Journey: http://glsl.heroku.com/e#794.0

Christmas tree: http://glsl.heroku.com/e#729.0

Modutropolis: http://glsl.heroku.com/e#327.0

The key to making this stuff work is writing "distance functions" that tell the ray marcher how far it is from the surface of an object. For more info on distance functions, see:

http://www.iquilezles.org/www/articles/distfunctions/distfunctions.htm

Upvotes: 1

datenwolf
datenwolf

Reputation: 162164

vec3 rayDirection  =   vec3( gl_FragCoord.x-250.0,gl_FragCoord.y-250.0 , 10.0);

Now i doubt that above method is right or wrong. Please give me some insights.

There's no right or wrong with projections. You could as well map viewport pixels to azimut and elevation angle. Actually your way of doing this is not so bad at all. I'd just pass the viewport dimensions in a additional uniform, instead of hardcoding, and normalize the vector. The Z component literally works like focal lengths.

I am also having doubt that do we need to construct geometry in OpenGL code while rayTracing in GLSL. for example if i am trying to raytrace a plane do i need to construct plane in OpenGL code using glVertex2f?

Raytracing works on a global description containing the full scene. OpenGL primitives however are purely local, i.e. just individual triangles, lines or points, and OpenGL doesn't maintain a scene database. So geometry passed using the usual OpenGL drawing function can not be raytraced (at least not that way).

This is about the biggest obstacle for doing raytracing with GLSL: You somehow need to implement a way to deliver the whole scene as some freely accessible buffer.

Upvotes: 2

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