Texture pixel screen pixel

[MolokoTheMole]

I need some help.
I have a 512x512 texture floating in front of the camera on a plane. Now I want to setup the camera (distance) so that 1 texture pixel is exactly 1 screen pixel. The screen resolution and FOV is given. How do I calculate the camera distance?

[rogerborg]

You can't do it with a perspective camera, since not all parts of the texture will be at the same distance.

If you really need this to be texel/pixel perfect, then you'll have to use an orthographic camera. See matrix4f::buildProjectionMatrixOrthoLH() and ICameraSceneNode::setProjectionMatrix().

If you build the projection matrix using the screen height and width, then your object sizes will correspond 1:1 to pixels, i.e. make your texture object the same height and width as its texture and it will come out close to 1:1 . Note that fp maths may produce some inconsistencies though.

Alternatively, since you have a texture, can't you just use IVideoDriver::draw2DImage() to draw it to screen? If you need the screen position of a 3d object, you can use ISceneCollisionManager::getScreenCoordinatesFrom3DPosition() to get it.

[BlindSide]

If you need to have stuff in front of the texture just use a screen quad with zwriteenable disabled.

[MolokoTheMole]

It's sort of a 2D/3D engine. Like Duke Nukem Manhattan. So it's 2D but I want it to look as best as possible from a 3D perspective with all the benefits like zooming, maybe slight tilting. So it doesnt have to be perfect but the textures on the map and player should approximate 1:1 correspondence with screen pixels.

--EDIT--
OK works with ortho camera. Thanks a lot!

[sudi]

My idea would be to use a vertex shader to place the quad.
I'm using the following shader:

Code: Select all

varying vec2 vTexCoord;
void main(void)
{
	vec2 Position;
	Position.xy = sign(gl_Vertex.xy);
	gl_Position = vec4(Position.xy, 0.0, 1.0);
	vTexCoord = Position.xy *.5 + .5;
}