3D and rendering
Mesh, normals, model, view and projection matrices, perspective, rasterisation, depth buffer, Lambert and Phong lighting, textures, ray tracing.
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A few cards from the deck
Mesh: what is it?
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The description of a 3D object by its vertices, joined into faces, most often triangles.
A triangle is always flat, hence its use: a graphics card can draw it very fast. Each vertex can carry a normal and texture coordinates.
The red triangle (depth 5) is drawn, then the blue one (depth 7) over the same pixels. With a depth buffer, which colour is seen?
- Red: its depth of 5 is smaller, so it is nearer
- Blue: it is drawn last and covers the red
- A mix of the two colours, weighted by the depths
- Blue: its depth of 7 is larger, so it is more visible
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Red: its depth of 5 is smaller, so it is nearer
The buffer compares depths, not drawing order: the blue fragment (7) is farther than the red one already written (5), so it is rejected. The result would be the same drawing blue first.
The … keeps, for each pixel, the depth of the nearest fragment already drawn; a new fragment only replaces it if it is ….
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The depth buffer keeps, for each pixel, the depth of the nearest fragment already drawn; a new fragment only replaces it if it is nearer.
Thanks to it, the order in which triangles are drawn does not change the image: there is no need to sort them from farthest to nearest.
Rendering pipeline: what is it?
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The sequence of stages that turns a 3D scene's vertices into pixels: vertex transformation, clipping, rasterisation, fragment computation, tests, image.
Each stage works on thousands of elements in parallel on the graphics card, which makes real-time display possible.