GPU Lightmapper

A simple OpenGL ambient light baker for OpenFrameworks.

About

ofxGPULightmapper combines different techniques to generate fast and smooth ambient shadows and textures.

Usage

// instance ofxGPULightmapper
ofxGPULightmapper lightmapper;

ofMesh mesh; 	// Mesh model
ofNode node;	// Model world transformation
ofFbo lightmap; // Lightmap texture
ofLight light;	// Sun light

// set up lightmapper and pass scene draw function
function<void()> scene = bind(&ofApp::renderScene, this);
lightmapper.setup(scene, 10); // 10 light pases

// setup lightmap
lightmapper.allocateFBO(lightmap);

// Bake scene light into the lightmap using geometry
lightmapper.updateShadowMap(light, {0,0,0}, 0.5, 10, 0.01, 20);
lightmapper.bake(mesh, lightmap, node, sampleCount);

// Draw geometry with baked light
lightmap.getTextureReference().bind();
mesh.draw();

VBO Mesh, Triangle Packer and UV spaces

The library can work both with ofMesh and ofVboMesh being the last one an advantage due the ability to create custom Vertex Buffer.

For Light baking, it's important that the geometry have a proper UV map. When the assets to be baked have no UV coords or the the UV texture coords are set for a LUT or share texture areas, ofxGPULightmapper allows generating a set the coordinates suitable for a Light Map and handles separately the coordinates of the model's textures and the coordinates of the lightmapper.

// Mesh model [VBO]
ofVboMesh mesh;
// Generate lightmap coords for the model
lightmapper.lightmapPack(mesh);

/*
 * baking
 */

// Draw geometry with texture and baked light
material.begin();
material.setUniformTexture("texture", texture, 0);
material.setUniformTexture("lightmap", lightmap.getTextureReference(), 1);
mesh.draw();
material.end();

Triangle Packer by @andsz https://github.com/ands/trianglepacker

Custom Light direction, AO and light bounces

For custom control of light direction, utilize the functions begin/end ShadowMap and begin/end Bake. The library will manage internally the shadow map and biased matrix.

This technique is useful for calculating ambient occlusion or performing light bounces.

/* AO baking */
ofLight light;

// For generic AO, light comes from everywhere
glm::vec3 lightDir = glm::sphericalRand(radius);
light.setPosition(lightDir);

// Update ShadowMap 
lightmapper.beginShadowMap(light, 10, 0.01, 100);
{	// draw the scene
    renderScene();
}
lightmapper.endShadowMap();

// Bake light
lightmapper.beginBake(lightmap, sampleCount);
{ 	// draw geometry
    node.transformGL();
    mesh.draw();
    node.restoreTransformGL();
}
lightmapper.endBake(lightmap);