# Vulkan Can't get my orthographic projection matrix to work

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Hello guys,

My math is failing and can't get my orthographic projection matrix to work in Vulkan 1.0 (my implementation works great in D3D11 and D3D12). Specifically, there's nothing being drawn on the screen when using an ortho matrix but my perspective projection matrix work fantastic!

I use glm with defines GLM_FORCE_LEFT_HANDED and GLM_FORCE_DEPTH_ZERO_TO_ONE (to handle 0 to 1 depth).

This is how i define my matrices:

m_projection_matrix = glm::perspective(glm::radians(fov), aspect_ratio, 0.1f, 100.0f);
m_ortho_matrix = glm::ortho(0.0f, (float)width, (float)height, 0.0f, 0.1f, 100.0f); // I also tried 0.0f and 1.0f for depth near and far, the same I set and work for D3D but in Vulkan it doesn't work either.

Then I premultiply both matrices with a "fix matrix" to invert the Y axis:

glm::mat4 matrix_fix =
{1.0f, 0.0f, 0.0f, 0.0f,
0.0f, -1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f};

m_projection_matrix = m_projection_matrix * matrix_fix;
m_ortho_matrix = m_ortho_matrix * matrix_fix;

This fix matrix works good in tandem with GLM_FORCE_DEPTH_ZERO_TO_ONE.

Model/World matrix is the identity matrix:

glm::mat4 m_world_matrix(1.0f);

Then finally this is how i set my view matrix:

// Yes, I use Euler angles (don't bring the gimbal lock topic here, lol). They work great with my cameras in D3D too!
m_view_matrix = glm::translate(m_view_matrix, -m_position);

That's all guys, in my shaders I correctly multiply all 3 matrices with the position vector and as I said, the perspective matrix works really good but my ortho matrix displays no geometry.

EDIT: My vertex data is also on the right track, I use the same geometry in D3D and it works great: 256.0f units means 256 points/dots/pixels wide.

What could I possibly be doing wrong or missing?

Big thanks guys any help would be greatly appreciated. Keep on coding, cheers.

Edited by HateWork

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m_ortho_matrix = glm::ortho(0.0f, (float)width, (float)height, 0.0f, 0.1f, 100.0f);

width and height here should not be the screen width and height, but rather the width and height in world space. The width usually depends om how ”zoomed in” you want to be, and height will be ”width * (resHeight/ resWidth)”

hope this helps

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On 1/10/2018 at 11:27 PM, Finoli said:

m_ortho_matrix = glm::ortho(0.0f, (float)width, (float)height, 0.0f, 0.1f, 100.0f);

width and height here should not be the screen width and height, but rather the width and height in world space. The width usually depends om how ”zoomed in” you want to be, and height will be ”width * (resHeight/ resWidth)”

hope this helps

Hi, thanks for your reply. I'm not setting any "zoom level", i'm 1:1 with the resolution. Any other examples of glm::ortho set the screen resolution, but no matter anyway, all the values I try fail.

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