1
vote
1answer
21 views

Camera world matrix to view matrix

I've been working on a game engine and I model every object in my scene graph as an "entity" this includes my camera. My camera therefore has a position and rotation in world space and at the moment ...
4
votes
2answers
173 views

How can I manually construct a right-handed orthographic projection matrix?

I need the formula to create a orthographic projection matrix. I am using GLM math libary and DirectX11. The reason I cannot use GLM to create it is because the NDC spaces are different between DX11 ...
3
votes
1answer
176 views

How to achieve cavalier projection using OpenGL fixed pipeline?

I want to make a quick demo program showing a cube, or a user loaded model, rotating in screen rendered with one of three projections: perspective, isometric and cavalier. Using the fixed pipeline, ...
3
votes
3answers
218 views

How do I disassemble a 3x3 transformation matrix into rotation and scaling matrices?

I have a transformation matrix that rotates and scales. Is there any easy way to disassemble it into the original rotation and scaling matrices? For instance: M = R * S; // I need f and h such that ...
2
votes
1answer
139 views

How do I check why is no output on screen?

I'm using OpenGL 3.3+, and I'm trying to create an orthographic projection to draw on screen. I have the model data in a buffer: X Y 0, 0 50, 100 100, 0 And I create my Model-View-Projection ...
3
votes
1answer
123 views

What are the performance and size tradeoffs of Eigen::Transform versus Eigen::Matrix4f?

We finished migrating from DirectXMath to the Eigen math libraries for our 3D-Game Engine last week for portability reasons. After implementing transformations with matrices as we know them, we found ...
1
vote
1answer
154 views

The correct way to transform a ray with a matrix?

Playing with XNA Triangle Picking Sample I found out that it does not work well if you scale the world matrix of the objects you want to pick. When I dug into the implementation I found this comment ...
0
votes
0answers
126 views

Alter a model-view-projection matrix

I have a model-view-projection matrix created based upon my camera. Is it possible to make alterations to it after it was computed to affect the corners of the resulting camera frustrum? For example, ...
0
votes
3answers
168 views

How can I properly rotate a 2D vector in the “flipped” XNA client space?

In my 2d XNA game, because SpriteBatch treats world space as client space and has positive Y axis down and negative up, I've built my game's world space with that coordinate system too. However, I've ...
0
votes
1answer
92 views

Multiplying matrices in HLSL

I have code that calculates a position like this in HLSL: output.ShadowPos = input.VertexPos; output.ShadowPos = mul(output.ShadowPos, gWorld); output.ShadowPos = mul(output.ShadowPos, ...
4
votes
5answers
1k views

How to rotate an object around world aligned axes?

I have a Vector3 which has an euler angle for each axis. Usually, when I want to create a rotation matrix I will use functions such as D3DXMatrixRotationX passing the respective angle from my ...
3
votes
1answer
238 views

How to move an object up and down like a wave?

I am trying to move my object up and down using cos and sin, but I have problem understanding how does the sin and cos work, so I can make my object move up and down like a wave frequently Init Time ...
0
votes
0answers
30 views

Is there a transformation or set of transformations that can approximate a “radial scale”?

Is there a way to, with matrices, scale something as if someone were opening a Japanese fan? I'm at a loss of what to call it, so pointers towards avenues of research would be greatly appreciated. If ...
2
votes
1answer
2k views

Combining rotation,scaling around a pivot with translation into a matrix

In short: I need to combine rotation (in the form of a quaternion), scaling around a pivot point along with translation into a transformation matrix. The long: I am trying to implement a proprietary ...
0
votes
1answer
192 views

Trying to convert as3 Matrix to C++ glm matrix

I am trying to convert a library called DragonBones to C++ Opengl which allows you to use Flash based skeletal animation. I'm almost done but I am running into a problem. I am trying to transform the ...
4
votes
3answers
305 views

Matrix multiplication - Scene Graphs

I wrote a MatrixStack class in C# to use in a SceneGraph. So, to get the world matrix for an object I am suposed to use: WorldMatrix = ParentWorld * LocalTransform But, in fact, it only works as ...
0
votes
2answers
331 views

Is this Rotation Matrix correct?

I'm having heavly troubles with setting up a View Matrix and a Projection Matrix. It simply doesnt work. So I think my problem is related to my rotationMatrix function. I'm using this tutorial to ...
3
votes
2answers
169 views

What kind of projection is ScreenX=X/Z, ScreenY=Y/Z?

I have an existing class which transforms 3D vectors and projects them on a 2D plane (Camera). The code is all written in C without help from an external library. To project a single vector (X,Y,Z) ...
2
votes
1answer
366 views

Negative scale in Matrix 4x4

After some rotations and to from quaternion conversions I get negative scale from Matrix 4x4, is it possible? I need that scale to draw sprite on screen so I get sprite flipped, how to deal with this ...
-1
votes
3answers
273 views

Directional light and matrix issues

I'm trying to implement basic directional lightning in OpenGL 3.3 by emulating the logic shown in this guide: http://www.arcsynthesis.org/gltut/Illumination/Tutorial%2009.html I do not understand ...
1
vote
2answers
232 views

Accumulating rotations for camera

It seems there are three ways to store a camera's rotation: in angles, view matrix or quaternion. I was using euler angles since when I used a matrix it had a tendency to accumulate rounding errors ...
7
votes
2answers
1k views

How can you extract orientation from a transformation matrix?

I have a 4x4 transformation matrix M, and I want to find out the shape of a sphere when transformed by M. (Sphere is at the origin and has radius 1.) I know I can find the center by just multiplying ...
1
vote
0answers
182 views

How do I implement a physics gun?

I'm currently trying to implement a physics gun for my game. What I want is for the entity to stay in the same position on the screen no matter how I wiggle the camera about, what is the correct way ...
1
vote
2answers
795 views

convert orientation vec3 to a rotation matrix

I've got a normalized vec3 that represents an orientation. Each frame of animation, an object's orientation changes slightly, so I add a delta vector to the orientation vector and then normalize to ...
8
votes
4answers
3k views

Staggered Isometric Map: Calculate map coordinates for point on screen

I know there are already a lot of resources about this, but I haven't found one that matches my coordinate system and I'm having massive trouble adjusting any of those solutions to my needs. What I ...
0
votes
1answer
244 views

Y Axis inverted on vertex output

I've got my project running and somehow it seems my vertex y components are inverted. 10 in the positive on Y goes down and 10 negative on the Y axis goes up. I can't find anything with the ...
4
votes
1answer
218 views

How to transform mesh components?

I am attempting to transform the components of a mesh directly using a 4x4 matrix. This is working for the vertex positions, but it is not working for the normals (and probably not the tangents ...
1
vote
1answer
204 views

Camera lookAt target changes when rotating parent node

have the following issue.I have a camera with lookAt method which works fine.I have a parent node to which I parent the camera.If I rotate the parent node while keeping the camera lookAt the target , ...
3
votes
2answers
452 views

3D rotation matrices deform object while rotating

I'm writing a small 3D renderer (using an orthographic projection right now). I've run into some trouble with my 3D rotation matrices. They seem to squeeze my 3D object (a box primitive) at certain ...
0
votes
1answer
926 views

Building View Matrix in Direct3D11

Am I doing it right? I converted this. m_ViewMatrix = XMMatrixLookAtLH(XMLoadFloat3(&m_Position), lookAtVector, upVector); to this one. XMVECTOR vz = XMVector3Normalize( lookAtVector - ...
2
votes
2answers
1k views

Rotating a child shape relative to its parent's orientation

When rotating a shape using a quaternion value I also wish rotate its child shape. The parent and child shapes both start with different orientations but their relative orientations should always be ...
3
votes
1answer
387 views

D3DXMatrixDecompose gives different quaternion than D3DXQuaternionRotationMatrix

In trying to solve this problem, I tracked down the problem to the conversion of the rotation matrix to quaternion. In particular, consider the following matrix: -0.02099178 0.9997436 -0.008475631 0 ...
3
votes
2answers
512 views

How to derive euler angles from matrix or quaternion?

Currently working on steering behavior for my AI and just hit a little mathematical bump. I'm in the process of writing an align function, which basically tries to match the agent's orientation with ...
3
votes
2answers
349 views

Rotating voxels in 3d space amongst the x axis

I have a very simple voxel engine and so far it works based on coordinates, e.g. x, y, z. I was wondering if there is a formula for rotating groups of voxels/coordinates from the x axis(e.g. [0, 1, ...
1
vote
1answer
172 views

Can't work out how matrix is applied to 2D vertices

I have a texture, some 2D vertices, and a matrix. The matrix is used to calculate the texture coordinates for each vertex, but the problem is that the matrix comes with absolutely no documentation and ...
0
votes
2answers
1k views

OpenGL matrix vs DirectX matrix

I'm working on an animation and model exporter from Maya to use within my game. Currently, models work perfectly, and animations have some issues with the joints. Since Maya works in an OpenGL ...
1
vote
3answers
334 views

Inverting matrix then decomposing gives different quaternion than decomposing then inverting the quat

I'm getting different signs when I convert a matrix to quaternion and invert that, versus when I invert a matrix and then get the quaternion from it: Quaternion a = Quaternion.Invert(getRotation(m)); ...
0
votes
1answer
424 views

Optimizing hierarchical transform

I'm transforming objects in 3D space by transforming each vector with the object's 4x4 transform matrix. In order to achieve hierarchical transform, I transform the child by its own matrix, and then ...
6
votes
1answer
232 views

Matrices: Arrays or separate member variables?

I'm teaching myself 3D maths and in the process building my own rudimentary engine (of sorts). I was wondering what would be the best way to structure my matrix class. There are a few options: ...
2
votes
1answer
331 views

Transform 3D vectors between coordinate systems

I've got 6 points in 3D space: A,B,C,D,E,F, that represent 4 vectors. AB is perpendicular to AC and DE is perpendicular to DF. I need to find a transformation matrix M, that transforms AB to DE and ...
2
votes
1answer
812 views

Is it possible to billboard a sprite using a transformation matrix?

None of the current topics on billboarding seemed to answer this question. But, given a sprite (or quad) that has it's own 4x4 transformation matrix a camera with a view matrix (a standard 4x4 ...
5
votes
1answer
384 views

How do I create weapon attachments?

My question is; I am developing a game for XNA and I am trying to create a weapon attachment for my player model. My player model loads the .md3 format and reads tags for attachment points. I am able ...
2
votes
2answers
490 views

3D Translation using only distance and angles

So I'm starting to foray into 3D game programming, but I've hit something of a snag. I have an object I want to move around. It should always move either forward or backward relative to its local Z ...
3
votes
2answers
544 views

Trying to understand 2D vector -> projection space conversion

I'm trying to understand how I can transform 2D vectors (x, y) to projection space. Something hasn't quite clicked for me yet. As per my previous question, here's the effect I'm trying to achieve: ...
6
votes
2answers
2k views

Matrix for 2D perspective

I'm trying to determine whether what I'm attempting to achieve is even possible mathematically. I'm obviously not a seasoned game developer so I'm having trouble even coming up with the terminology to ...
6
votes
3answers
955 views

Arbitrary projection matrix from 6 arbitrary frustum planes

A projection matrix represent a tranformation from the camera view space to the rendering system clip space. In other words, it defines the transormation between a 6-sided frustum to the clip cube. ...
3
votes
1answer
391 views

Confused about order of operation when using a Matrix in XNA, C#

Here are two different pieces of code This is what I started with Vector2 hold = Vector2.Transform(pos1, mat1); Matrix inv = Matrix.Invert(mat2); Vector2 pos2 = Vector2.Transform(hold, inv); And ...
2
votes
1answer
422 views

How to linearly transform vertices for large coordinate systems

Alright, so I'm working on a space game and well, I want it to have a lot of space! So I need a large coordinate system and for my rendering pipeline to not suffer from "vertex jittering" due to ...
5
votes
2answers
985 views

What's a pre-multiplied 4x4 matrix?

I'm using a 3d game engine, that uses a 4x4 matrix to modify the camera projection. The matrix is in the regular 4x4 format: r r r x r r r y r r r z - - - zoom The description for the ...
4
votes
3answers
5k views

How to get translation from view matrix

How can I retrieve the camera's world-space position from its view matrix? The only answers I've seen to this question suggest the translation is in the last row/col but this wouldn't work since the ...