Minor issue with Field rendering and env maps

Blender's renderer and external renderer export

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kid_tripod
Posts: 57
Joined: Sun Dec 15, 2002 10:52 pm

Minor issue with Field rendering and env maps

Postby kid_tripod » Wed Aug 20, 2003 1:30 pm

Hello!
I've been doing some work which needs field rendering. And for reasons I won't go into I don't want a time difference between fields . . .

the problem is I also have an envmap, and Blender insists on recalculating it for both fields, even though it will be the same, so if someone could implement a simple check I'd be grateful. It would cut my render time in half.

Secondly, field rendering appears to produce some really nasty shadow artefacts (on static scenes). I'll try posting one soon.

Cheers

Kt

(apologies if the wrong forum, I'm still not sure about round here!)

LukeW
Posts: 64
Joined: Mon Mar 03, 2003 1:14 pm

Postby LukeW » Sun Aug 24, 2003 9:23 am

kid_tripod:
the problem is I also have an envmap, and Blender insists on recalculating it for both fields, even though it will be the same, so if someone could implement a simple check I'd be grateful. It would cut my render time in half.

The envmaps will be different during field rendering - unless you have the "X" near the fields button selected.... the tooltip for "X" says "disable time difference for field calculations." Normally when you do fields, it doubles the framerate... so if you have a PAL tv, it shows 50 frames per second (at half resolution) - or 25 frames per second at full resolution. NTSC is 60 or 30 frames per second. The second field in the render is the inbetween frame... so if you're rendering frame 140, the second field (e.g. the odd lines) will be frame 140+1/2.... (unless you have "X" selected, then it will just base it on frame 140)
If there is no movement in your scene though, then the envmap won't change... but this is also true if you didn't have field rendering....

For scenes that don't have much movement, I think it would be good if envmaps were only rendered once per frame, like you said (though in field rendering there are really 2 [interleaved] frames...) and maybe people could choose to have the envmaps updated every 2 frames or 5 frames, etc.

I think I might have come across the shadow artifacts you've talked about (I render using fields a lot)... it happens when I have the softness and bias really low... so I increase them to get rid of it. BTW, what do you mean by a "static scene" - I thought Blender did shadows for moving and non-moving objects exactly the same.

kid_tripod
Posts: 57
Joined: Sun Dec 15, 2002 10:52 pm

Postby kid_tripod » Mon Aug 25, 2003 12:46 pm

I have had the 'X' pressed, since I need to have no time difference for my use for it, but it then renders the (same) envmap twice for each frame.

EDIT: as regards the 'static scene' just to say that I encountered the artefacts without movement, whereas had not 'X' been pressed I'd know you'd get the breakup lines from fields etc. I'll try your ideas out for that, although I must confess I've never worked out what the 'bias' control actually does.

LukeW
Posts: 64
Joined: Mon Mar 03, 2003 1:14 pm

Postby LukeW » Mon Aug 25, 2003 1:12 pm

kid_tripod wrote:I have had the 'X' pressed, since I need to have no time difference for my use for it, but it then renders the (same) envmap twice for each frame.

EDIT: as regards the 'static scene' just to say that I encountered the artefacts without movement, whereas had not 'X' been pressed I'd know you'd get the breakup lines from fields etc. I'll try your ideas out for that, although I must confess I've never worked out what the 'bias' control actually does.

You should render it without fields... if you need to import it into a video program, etc, just say it is "progressive" (or it has no field order rather than upper or lower field first). Also it might take less time to render even if there wasn't that envmap problem.
Maybe the bias is the sensitivity to detecting objects blocking the light or the contrast or something.


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