Sprites

[Baker]

[mh]

[Spike]

changing matricies is generally quite expensive, as a simple matrix change will break your batch after every single sprite.
this is true even with glBegin, as the driver will generally auto-batch those for you.
if you do submit a matrix you're uploading a 4*4 modelview matrix, vs the 4 * 3 vertex coord floats you'd otherwise upload.
at the end of the day it makes little difference.

besides, the up+right stuff is basically a matrix anyway.

[mh]

And when you think about it, sprites actually share a lot of properties with particles (especially if your engine does sexy textured particles) so a reasonable approach may be to amalgamate the two.

[Baker]

[frag.machine]

[leileilol]

now what if those sprites supported scaling and were integrated into the particle system.......... in software?

Heretic II and Half-Life did this.

[Baker]

3D Ortho!

I'm sure Spike will find this anti-climatic since Quake III throws models into the HUD --- and I didn't actually check out Quake 3 source, but looked a little @ "csqctest" but mostly ignored what I saw not liking it.

Fun part of this is that 3D ortho really requires having an open-source version of glFrustum to inspect the matrix calculation (like in Remake Quake engine) or there are glFrustum open source codes out there at github for various stuff including, say, the PSP (just coincidence that the PSP version is easy to find). And you need gluUnproject to validate your expectations (otherwise it would be near impossible hit and miss trying to guess). Had to muck around with the FOV values to get a number that created nice matrix values (you know, like 1 or some number that is an obvious X/Y) versus some floating point # with a crapton of digits. Then write a couple of functions translating the ortho coordinates you want to pretend you are using to the ones where Z = 1.

But the fun thing, and I haven't done this yet: but I should be able to translate, rotate, scale the modelview matrix at will. Which means I can draw 2D and spin it, rotate it, bob it up or down. Or any kind of 3D treatment I want. While I haven't done any 3D effects, I certainly have 3D ortho working after 2 hours of tweaking, inspecting, planning (and a few failures where concepts failed).

Kind of nice how the possibilities increase when you know more stuff and actually reach the threshold of understanding topics that were once out-of-reach

/ I wasn't actually shooting for 3D ortho when I asked the sprite question ... but the discussion about not recalcing the matrix with each sprite/particle got me thinking of 2D vertices and I kind of spontaneously thought of something I wanted to try.

[mh]

Nothing special about glFrustum - the matrix it calculates is given here: http://msdn.microsoft.com/en-us/library ... 85%29.aspx

[Baker]