tinyrenderer | A brief computer graphics / rendering course | Graphics library
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kandi X-RAY | tinyrenderer Summary
A brief computer graphics / rendering course
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I wrote a program that takes in entry some points, expressed in 3D coordinates and that must be drawn in a 2D canvas. I use perspective projection, homogeneous coordinates and similar triangles to do that. However, my program does not work and I actually don't know why.
I followed two tutorials. I really understood the geometrical definitions and properties I have read. However, my implementation fails... I will write references to these both courses little by little, to make your reading more confortable :).Overview : geometrical reminders
The perspective projection is done following this workflow (cf. these 2 courses - I wrote pertinent links (HTML anchors) further down, in this post) :
Definition of the points to draw, expressed according to the world's coordinates system ; Definition of the matrix of projection, which is a matrix of transformation that "converts" a point expressed according to the world coordinates system into a point expressed according to the camera's coordinates system (NB : this matrix also can be understood as being the camera)
Product of these points with this matrix (as defined in the adequat part, below) : the product these points results in the conversion of these points to the camera's coordinates system. Note that points and matrix are expressed in 4D (concept of homogenous coordinates).
Use of similar triangles concept to project (only computing is done at this step) on the canvas the in-camera-expressed points (using their 4D coordinates) : they are now expressed in 3D (the third coordinate is computed but not actually used on the canvas)
Last step : rasterization, to actually draw the pixels on the canvas (other computing AND displaying are done at this step).
Well, I want to draw a cube but it doesn't appear. The projected points seem to be drawn on the same coordinates.
Instead of my cube, only one black pixel is visible.
NB : since X11 is not activated on Scastie, the window I want to create won't be shown.
Perhaps the problem is bound to the entries ? Well, I give you them.Cube's points
Ref. : myself...
ANSWERAnswered 2018-Feb-27 at 22:55
toInt on a normalized device coordinate (meaning that the valid range is [0, 1]):
I'm learning a short course "How OpenGL works: software rendering in 500 lines of code" on GitHub. In lesson 2, the author is teaching us how to fill a triangle with color. He comes up with two methods:
Enumerate all the horizontal segments within the triangle, and draw these segments. The author's code is as follows....
ANSWERAnswered 2017-Feb-28 at 07:18
Barycentric coordinates are used to interpolate or "smear" values at each vertex of the triangle across the triangle. For example: if I define a triangle ABC, I can give each vertex a color, Red, Green, and Blue respectively. Then as I fill out the triangle, I can use the barycentric coordinates (alpha, beta, gamma) to get a linear combination P = alpha * Red + beta * Blue + gamma * Green to determine what the color at a point inside the triangle should be.
This process is highly optimized and built into GPU hardware. You can smear any values you'd like, including normal vectors (which is often used in per-pixel lighting computations), so it is a very useful operation.
Of course, I have no idea what your teacher is thinking, but I'd hazard to guess that in a future lesson they might talk about that so the second algorithm naturally leads into that discussion.
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