I'm looking for to simulate the reflection effect using ray tracing on GLSL, however I could not find good references, examples or tutorial related to this topic. When I got some interesting data, the method is limited for specific object's surfaces (e.g. sphere, box, cylinder...) and it needs to know object's position and radius; it is not my case. I also know the GLSL does not support recursive functions, but as far as I know the ray tracing can be done iteratively.

My goal is to simulate the reverberation process for an acoustic sensor as follows: primary reflections by rasterization; and secondary reflections by ray tracing. When a ray hits the object's surface, the distance and normal values are measured.

My scene with all objects is modeled using OpenSceneGraph, and I have used GLSL to handle the normal and position data from the viewpoint on GPU.

Follows below my current GLSL code. At this moment, I am able to calculate the ray parameters (world position and direction vector values, for each pixel), however I do not know how to calculate the data when a ray hits a surface.

Thanks in advance. Any help is very much welcome.

Vertex shader:

Code :#version 130 uniform mat4 osg_ViewMatrixInverse; out vec3 positionEyeSpace; out vec3 normalEyeSpace; uniform vec3 cameraPos; // ray definition, with an origin point and a direction vector struct Ray { vec3 origin; vec3 direction; }; void main() { gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex; // world space mat4 modelWorld = osg_ViewMatrixInverse * gl_ModelViewMatrix; vec3 positionWorldSpace = vec3(modelWorld * gl_Vertex); vec3 normalWorldSpace = mat3(modelWorld) * gl_Normal; // eye space positionEyeSpace = vec3(gl_ModelViewMatrix * gl_Vertex); normalEyeSpace = gl_NormalMatrix * gl_Normal; // calculate the reflection direction for an incident vector vec3 I = normalize(positionWorldSpace - cameraPos); vec3 N = normalize(normalWorldSpace); vec3 reflectedDirection = normalize(reflect(I, N)); }

Fragment shader:

Code :#version 130 in vec3 positionEyeSpace; in vec3 normalEyeSpace; uniform float farPlane; uniform bool drawNormal; uniform bool drawDepth; out vec4 out_data; void main() { vec3 nNormalEyeSpace = normalize(normalEyeSpace); vec3 nPositionEyeSpace = normalize(-positionEyeSpace); float linearDepth = sqrt(positionEyeSpace.x * positionEyeSpace.x + positionEyeSpace.y * positionEyeSpace.y + positionEyeSpace.z * positionEyeSpace.z); linearDepth = linearDepth / farPlane; // output the normal and depth data as matrix out_data = vec4(0, 0, 0, 1); if (linearDepth <= 1) { if (drawNormal) out_data.z = abs(dot(nPositionEyeSpace, nNormalEyeSpace)); if (drawDepth) out_data.y = linearDepth; } gl_FragDepth = linearDepth; }