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HaplessHalfwit
04-06-2017, 02:54 PM
Hey all...

I was wondering if anyone could tell me where I am going wrong when implementing a perspective matrix.
The math for creating the matrix appears to be correct from what I can tell, however the end result is a stretched out distorted shape that takes up the entire screen, which is a far cry from the basic cube i had rendering before.
This is purely an educational exercise, hence why I have laid out the matrix deceleration this way..

Creation



static Matrix4 CreatePerspectiveMatrix(float fov, float aspect, float zNear, float zFar) {
Matrix4 r;

float tanThetaOver2 =(float)tanf(ToRadians(fov / 2));
float zRange = zNear - zFar;
float zTotal = zNear + zFar;

r.m[0][0] = 1.0f / (tanThetaOver2); r.m[0][1] = 0; r.m[0][2] = 0; r.m[0][3] = 0;
r.m[1][0] = 0; r.m[1][1] = aspect / tanThetaOver2; r.m[1][2] = 0; r.m[1][3] = 0;
r.m[2][0] = 0; r.m[2][1] = 0; r.m[2][2] = zTotal/zRange; r.m[2][3] = 2 * zFar * zNear / zRange;
r.m[3][0] = 0; r.m[3][1] = 0; r.m[3][2] = -1; r.m[3][3] = 0;

return r;
}


Implementation


void Game::Draw()
{
m_display->SwapBuffer();
m_renderer.Draw();
m_shader.Bind();
Matrix4 mtxModel = m_transform.GetMatrix();
Matrix4 mtxProjection = Matrix4::CreatePerspectiveMatrix(60.0f, m_display->GetAspectRatio(), 10.0f, 1000);
Matrix4 mtxModelProjection = mtxProjection * mtxModel;
m_shader.SetSharderMatrixUniform("transform", mtxModelProjection);
m_renderer.DrawMesh(m_mesh);
m_shader.UnBind();
//assert(glGetError() == GL_NO_ERROR);
}


End result
2353

Thanks for reading,

Any help available would be greatly appreciated .

GClements
04-07-2017, 11:33 AM
Your matrix looks fine, but it's in row-major order. OpenGL defaults to column-major order, so it needs to be either explicitly declared as being in row-major order, or transposed.