OpenGL 3.x Rotation Problem

[Brainer]

Sorry, but the code proposed by you doesn't not seem to work. It doesn't even display the triangle.

[User137]

How about:

ModelView := MatrixMultiply(MatrixMultiply(ProjMat, ModelView2), Cam);

[Brainer]

Nope, it's still the same. In both cases nothing's even displayed.

[Brainer]

I noticed that there is a problem with the math I'm using to create the matrices. I noticed that when I tried to transpose the matrix using glUniform and my custom-build function. They produced different results.

Does anyone have any decent Pascal math library with matrix functions (I'd also like to have functions for calculating transformation matrices included)?

[JSoftware]

I just took a look at your transformation matrix code. It seems some of the signs are wrong when you calculate the rotation matrix. I'll take a look later when I'm drunk enough to understand this matrix stuff

[JSoftware]

This is the matrix that I calculated. It might be that it's for a righthand coordinate system though. That might be why

[              cos(ty)*cos(tz),             -cos(ty)*sin(tz),     sin(ty),0]
[ cos(tx)*sin(tz) + cos(tz)*sin(tx)*sin(ty), cos(tx)*cos(tz) - sin(tx)*sin(ty)*sin(tz), -cos(ty)*sin(tx),0]
[ sin(tx)*sin(tz) - cos(tx)*cos(tz)*sin(ty), cos(tz)*sin(tx) + cos(tx)*sin(ty)*sin(tz), cos(tx)*cos(ty),0]
[0,0,0,1]

[Brainer]

Thanks. I did the corrections.

But it's still the same. I even tried changing a little the rendering code:
[code=delphi]
{ .: MatrixLookAt :. }
function MatrixLookAt(const From, At, Up: TVector): TMatrix;
var
xAxis, yAxis, zAxis: TVector;
begin
zAxis := VectorSubtract(From, At);
zAxis := VectorNormalize(zAxis);
xAxis := VectorCrossProduct(Up, zAxis);
xAxis := VectorNormalize(xAxis);
yAxis := VectorCrossProduct(zAxis, xAxis);

with Result do
begin
_11 := xAxis.X;
_12 := yAxis.X;
_13 := zAxis.X;
_14 := 0.0;

_21 := xAxis.Y;
_22 := yAxis.Y;
_23 := zAxis.Y;
_24 := 0.0;

_31 := xAxis.Z;
_32 := yAxis.Z;
_33 := zAxis.Z;
_34 := 0.0;

_41 := VectorDotProduct(VectorScale(xAxis, -1.0), At);
_42 := VectorDotProduct(VectorScale(yAxis, -1.0), At);
_43 := VectorDotProduct(VectorScale(zAxis, -1.0), At);
_44 := 1.0;
end;
end;

{ .: TMainForm.Render :. }
procedure TMainForm.Render;
var
ProjMat, Cam, ModelView, Model: TMatrix;
begin
glViewport(0, 0, ClientWidth, ClientHeight);
glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT);

// Projection update
if (ClientHeight <= 0) then
ClientHeight := 1;
ProjMat := MatrixProjection(40.0, ClientWidth / ClientHeight, 0.1, 1000.0);

// Camera transformations
Cam := MatrixLookAt(VectorNegate(Camera.Pos), VectorCreate(0.0, 0.0, -1.0),
VectorCreate(0.0, 1.0, 0.0));
Model := MatrixTransform(VectorCreate(0.0, 0.0, 0.0),
VectorCreate(0.0, TriangleRot, 0.0), VectorUniform(0.5));
ModelView := MatrixIdentity;
ModelView := MatrixMultiply(MatrixMultiply(Model, Cam), ProjMat);

// Update the shader
glUniformMatrix4fv(glGetUniformLocation(ShaderMana ger.GLSLPrograms['minimal'].
ProgramHandle, 'mvpmatrix'), 1, ByteBool(GL_FALSE), @ModelView);

// Render the triangle
glBindVertexArray(TriangleVAO);
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexArray(0);
end;
[/code]
The new code displays the triangle, but the translation doesn't work correctly. When I translate the triangle with an arrow key, it doesn't change its position. Once I strafe and then try to move it forward, it suddenly accelerates. Clearly it's a problem with the matrix I pass to the shader, but where is the bug hidden? The function was taken from LEAF2 engine - I hoped it was a good one.

[User137]

The LookAt function is definitely off. Was doing my Matrix lib today based on GLScene and tested this on the way. Lib itself works perfectly when i rotate object with mouse with my functions. It's when i set camera with this lookAt it doesn't go to right place.

[pascal]// This doesn't work
cam:=MatrixLookAt(Vector(0,0,-3),Vector(0,0,0),Vector(0,1,0));

// This works
cam:=NewMatrix;
TranslateMatrix(cam,Vector(0,0,-3));[/pascal]

Edit: I also used your matrix multiplication function so it means they are read same way GLScene made 1 line for each 16 array elements, 2 x for loop is more compact.

[Brainer]

Hm, okay. Thanks for your feedback.

So you suggest using normal transformation functions instead of LookAt, right? But this approach doesn't work, either. The first snippet I posted contained the MatrixTransform function. It was wrong at first, but JSoftware provided us with a new matrix and I modified the code. Nevertheless, the effect is still far from what's desired.

Maybe it's something wrong with the shader? Maybe I'm looking for a bug in a wrong place?

[paul_nicholls]

Hi Brainer,
A while ago I was fiddling around with creating software OpenGL routines (for my gp2x handheld), and I DID get something basic working.

I could emulate exactly how OpenGL did its rendering with regards to transformations.

I have a unit you could look at which includes all my OpenGL transformations, etc. but it is 1307 lines long...

Is it ok if I post it here?

Perhaps it may help you with your matrix issues...

cheers,
Paul