Raytracing

Set the camera at a point in space and the direction that it is facing. At a distance D set a viewport through which the camera see. The viewport defines the part of the scene to be render on the canvas which is a memory buffer sized for a certain resolution. 

The scene is a 3-D space which contains objects. Each object (like a sphere) is model mathematically by equation. Each object has a distance away from the camera (D1). Object behind the viewport will be raytraced and rendered on the canvas. From the camera position to each grid on the view port forms a vector. Extend the vector directionally intent hit an object in the scene (intersect). Paint the grid with the color of the object. As the one t is 3-D, the ray may intersect multiple points on the object. Only the front most point will be painted.