Simple 3D transform in 2D GL_Ortho ?

Graphics and GPU Programming Programming

Started by FlyingSolo March 31, 2015 11:58 PM

2 comments, last by jeskeca 8 years, 12 months ago

FlyingSolo

117

Author

March 31, 2015 11:58 PM

I'm in a bit of a pickle and would really appreciate some help with this.

I've got a large and complex project which has strictly been a 2D affair - until now.

I need to display what I'll describe as a "Clock Face" as though it was lying on the table in front of you. Looking at it from this viewpoint it becomes elliptical. I can't draw a simple ellipse to emulate this though since I need the clock face (and the texture on it) to rotate.

Can anyone offer me some hope that this can be achieved?

Many thanks :-)

Zylann

204

April 16, 2015 11:34 AM

Maybe you can pre-transform the vertices of your model before drawing (so it will look like a 3D ellipse), and animate the UVs so you can make it visually rotate.

If you want the model itself to rotate, you'll have to use a vertex shader and appropriate perspective projection matrices.

Coding stuff

FlyingSolo

117

Author

April 16, 2015 11:45 PM

Thanks for the suggestions, but sadly it would seem unlikely we can achieve what we wanted.

Wishing now I'd gone 3D in the first place!

Thanks :-)

jeskeca

676

April 17, 2015 04:37 PM

If you want perspective projection, you'll want to render it in 3d.

If you want to keep your main scene 2d ortho, you can render a 3d perspective object to a texture and then splat it into your scene.

It's also pretty easy to convert a flat 2d ortho into a matte plane of a 3d projection.. But to render 3d objects against it you'll need a rational approach to z depth occluding.

Simple 3D transform in 2D GL_Ortho ?

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