Let me see if I can make myself clear, and if I’ve got the correct forum.
Since I can’t seem to get a handle on 2.5, I must continue to use 2.49b’s Halo particle systems to produce effects like fire and smoke. On my ancient machine, I doubt fluid-based smoke would bake in any reasonable amount of time anyway.
My question is this: when I have a particle system using a Halo material, and I have HaloTex on, I imagine I can turn off “Color” and then turn the “Alpha” option on for the texture (the second, yellow setting). This makes the Halo, with Hardness set to 1, have a rough-edged shape that makes much more convincing (and render-heavy) fire or smoke effects.
When I use Halos like this, I always make an IPO system to turn Alpha down to 0 over a length of time (usually the equivalent of four seconds or so). And this is where the problem comes in. Sometimes, the particles work like I expect them to; while still textured, the Halos gradually fade away and disappear. However, other times, they do not fade at all, persistently remaining at the same Alpha value as the texture dictates from the mapping options.
What causes the change between working correctly and not is a mystery to me. The only common thread is that this Alpha mapping setup only seems to work on textures with solid black around the four corners (almost as if Blender calculates transparency data based on the upper or lower left corner’s pixel color). However, I could be completely wrong about this.
That’s more or less what’s stumping me presently, along with two other particle-related problems:
1: Despite the fact that I set the IPO curve to reduce Alpha to 0 on frame 60 (which it does correctly, if the Color settings are telling the truth), the particles always disappear at exactly half that time (i.e., the particles are fully transparent and invisible on frame 30, but continue to “live” and eat render time until they die 30 frames later).
2: I have no clue how to rotate Halos. I want my clumpy puffs of fire to rotate randomly for a more satisfying “churning” effect, but nothing I’ve done in the rotation settings has had the slightest effect.
I’ve considered switching to billboards for effects particles, but without Soften and Addition they’ll never look as good.
Well, I’m off to bed. Take your time. I’m grateful for any insight you can offer.