Multiple shaders, objects and materials with OOP

Question

I am using GLSL shaders in a small Java OpenGL project I am making, and I am trying to come up with a well-written object-oriented way of organising my code. So far, I have a class called Model, which can contain multiple meshes, each of which has its own texture and material (a material being a set of parameters to describe ambient, diffuse, specular, blending, etc.). In order to achieve this, I understand that I could pass uniform variables to the shader every time I need to change material. However, the drawing takes place in the model's draw() method. Does that mean that each instance of the Model class needs to have a particular shader associated with it?

Also, I have a Camera class, which produces a matrix that will transform vertices simulate the camera's pitch, yaw, and position. This matrix then needs to uploaded to the shader as the view matrix. Doesn't that mean that I need to upload this matrix to every shader that I use? So if each Model can have its own shader, how can I upload the camera's view matrix to all of them? And even so, isn't it inefficient for every single model to have its own shader? If you wanted to draw a certain model lots of times, then you would be use()ing the shader and uploading a matrix to the shader every time you drew it.

I'm really struggling to come up with an object-oriented solution that links multiple shaders, multiple objects and multiple materials. Any help is appreciated.

Iggy Iggy · Accepted Answer · 2014-12-08T21:45:35

Modern OpenGL requires you to write vert/frag shaders in order to render anything, so it would be a safe bet to have the Material stored with the Model object. You could perhaps have a Default Material if none was linked with a model object - kind of like missing textures or models.

Rendering engine architecture is a big concept in general and I don't fully understand some things myself, but so far I quite like how THREE.js went about it structuring it. Of course it's made in javascript, but the ideas are quite translatable to other languages. You should look into it.

scene = new THREE.Scene();

camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 1, 10000 );
camera.position.z = 1000;

geometry = new THREE.BoxGeometry( 200, 200, 200 );
material = new THREE.MeshBasicMaterial( { color: 0xff0000, wireframe: true } );

mesh = new THREE.Mesh( geometry, material );
scene.add( mesh );

renderer = new THREE.CanvasRenderer();
renderer.setSize( window.innerWidth, window.innerHeight );

Multiple shaders, objects and materials with OOP

2 Answers