9
votes
Accepted
lookAt with orthographic camera (gl-matrix)
When I use the identity view matrix, I can see my model, but when I use LookAt, it is not visible. How can I see my model using ...
- 9,059
7
votes
Accepted
How to mirror/reflect/flip a 4D transformation matrix
To get a transformation matrix equivalent to the one you have, but reflected across a major axis you can compose it (multiply it by) a reflection matrix.
That is, if you have your input matrix M and ...
- 28.3k
7
votes
Accepted
Finding islands from array
This is a standard computer science problem called connected component search.
You can solve it in time linear in the number of cells using iterated depth-first / breadth-first search or a flood fill ...
- 141k
6
votes
Accepted
How to convert a 4x4 matrix transformation to another coordinate system?
This is as easy as writing your old coordinates in terms of the new ones.
We want +x to map to +x (1, 0, 0)
We want +y to map to +z (0, 0, 1)
We want +z to map to -y (0, -1, 0)
We want the fourth, ...
- 141k
5
votes
How does glm::lookAt produce a View Matrix?
Alright so upon looking into it further, here's how glm::lookAt produces a View Matrix:
Make a row-major ordered 4x4 Translation Matrix by negating the camera position, c:
...
- 71
4
votes
Accepted
Why do these DirectXMath functions seem like they return column-major matrics?
You posted a column-major version of the translation matrix for (1,1,-1):
1.0 0.0 0.0 1.0
0.0 1.0 0.0 1.0
0.0 0.0 1.0 -1.0
0.0 0.0 0.0 1.0
...
- 3,972
4
votes
From 3d rotation, snap to nearest 90 directions
For anyone in the future looking for a solution to this using Unity/C#, here is an implementation I made based on Steve's answer:
...
4
votes
Accepted
Normal Matrix in plain English
You need to use a different matrix to transform your normal vectors when your model's transformation might include non-uniform scale.
When we stretch a shape along, say, just the y axis, the y ...
- 141k
4
votes
Accepted
Difference between World matrix and Model matrix?
The names "world matrix" and "model matrix" are just terminology, and are not 100% standardised, so depending which source you read you may see them being used to refer to a number ...
- 20.3k
4
votes
Accepted
How do I create a localtoworldmatrix and worldtolocalmatrix in Godot?
In Godot a Transform3D has no concept of local or world. They are transformations between spaces, and what those spaces are depend on how you use them.
For a ...
- 28.3k
3
votes
Accepted
How to Convert a Z Up Matrix to a Y Up Matrix?
Anything you'd do would effectively be a rotation.
That's the matrix to apply to your other matrix:
[1 0 0 0]
[0 0 -1 0]
[0 1 0 0]
[0 0 0 1]
Alternatively:
<...
- 12.1k
3
votes
Accepted
3d isometric projection matrix?
You should try having a separate camera and projection matrix, since isometric projection is just ortographic with a very specific camera placement.
If you are using a modern matrix library (you ...
- 15.1k
3
votes
Should calculations be done on the CPU or GPU?
A few rules of thumb around this, if the calculation only needs to be done once and applies to the entire object, then you will get best bang for buck calculating it prior to loading onto the GPU. IF ...
- 1,190
3
votes
Accepted
Should 3D transformations be represented by a 4x4 matrix or a 3x4 matrix?
Since 3D transformations are represented by 4x4 homogeneous matrices
Correction: Might be represented by 4x4 matrices ;)
Now I can see how this would be a great optimization at first as it increases ...
- 599
3
votes
Accepted
Invert parent transform (doesn't work for combination of rotation and scale)
A 4x4 homogeneous matrix can represent any affine transformation. That is, any combination of:
Translation by any offset
Rotation around any axis by any angle
Scale along multiple arbitrary axes by ...
- 141k
2
votes
Problem Rendering a Wireframe Cube and Grid with DirectX 11
D3D11_INPUT_ELEMENT_DESC inputElementDesc[] =
{
{"POSITION",0,DXGI_FORMAT_R32G32_FLOAT,0,0,D3D11_INPUT_PER_VERTEX_DATA,0}
};
You need to change the format to ...
2
votes
TRS Matrix between 2 points
The question hardly makes sense for points, since, if I'm not mistaken, there are infinitely many matrices that would fit.
If you mean 'objects' rather than 'points', then the answer simple:
You ...
- 2,054
2
votes
Is clipping done before or after projection?
The projection matrix describes the mapping from 3D points of a scene, to 2D points of the viewport. It transforms from eye space to the clip space, and the coordinates in the clip space are ...
- 321
2
votes
Accepted
Why does a translation matrix need an extra row?
If you're doing all your transformation with a single matrix, and you don't need to do any other computation with that matrix or the output vectors, then you're right, you don't need the extra row.
...
- 141k
2
votes
Display object at different position
Yes, you have several options here:
Use Graphics.DrawMesh (or one of its variants) to manually submit a drawing call, without a renderer component at all. You can provide your own position & ...
- 141k
2
votes
How do Axis-Aligned Bounding Boxes update with rotations?
Given an original axis-aligned bounding box and a transformation matrix, you can compute a new axis-aligned bounding box from the extents of the original box, transformed by the matrix, like so:
<...
- 141k
2
votes
Accepted
What exactly does XMMatrixPerspective{L,R}H do?
The DirectXMath library is all inline so you can look directly at the source.
For example, here is the C version of XMMatrixPerspectiveLH:
...
- 3,972
2
votes
Accepted
Translate operation is rotating?
Your matrix is row major, so you should transpose it in order to get behaviour you expect, since OpenGL memory layout is more column-major friendly, because translation is located in the memory at the ...
- 1,433
2
votes
Accepted
Which is a better way for moving 3d objects in OpenGL?
Mix of the both: move object for game logic, move the origin/camera (modify modelview matrix) for drawing.
As you said, recalculating the vertex buffer every frame is not going to be efficient, to ...
- 371
2
votes
Accepted
matrices and nesting hierarchy with game objects
Inheritance of transformation is the main reason we like to use transformation hierarchies in game scenes.
If I want to move a car, it's convenient that I can simply move the body/root of the car, ...
- 141k
2
votes
Accepted
Scaling a rotated child with parent-child transforms
After some experiments, I figured this out, and as was noticed in the comments to my question it was not to do with my matrix multiplication order, but rather something else entirely.
After ...
- 141
2
votes
Accepted
What is the signifigance of the Dot Product in World to Local Transformations?
This is a vector projection. Dotting a vector like AgentPosition with a unit direction vector like AgentHeading or ...
- 141k
2
votes
Rotate Object in world space - Raytracing
As mentioned in the comments, rotation in 3 dimensions has 3 degrees of freedom (you can think of them like yaw, pitch, and roll), but a unit vector in 3 dimensions has only 2 degrees of freedom (...
- 141k
2
votes
Accepted
Random 100x100 map using all levels from 1 to 100
To ensure all castles 1-100 are present, simply shuffle an array containing all the numbers 1-100. You can either do this once when you first generate the map and then hold onto it, or you can use a ...
- 1,154
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