View Full Version : XSI's Preview render

09 September 2004, 05:13 AM
All the renders done by the preview function: are they equivalent in quality to what you'd get if you just render an image straight to file?

(this is so that when I decide to render some quick image, i can just preview-render it and save it to a location i wanted to save it to instead of rendering it to file, then editing/renaming that file)

09 September 2004, 05:47 AM
Yes... Preview Rendering and Render Region are exactly the same as Real Rendering.

09 September 2004, 08:27 AM
Yes. But first look in to the Preview options.. to use a Pass Render Options no teh default -2,0.

09 September 2004, 09:44 PM
Looks like it's working but there's one little thing I noticed:

I render or save to TGA, and the same image that gets rendered direct to TGA is 3 megs while the same image saved to TGA from the preview render window is 1 meg. Why the difference?

09 September 2004, 09:56 PM
i would guess that the anti-aliasing/sub-sample settings in your preview do not match your final render settings, producing an image of slightly lower quality and greater "compressability" in preview mode.

either that, or your preview is getting saved as a compressed TGA and your final render is uncompressed.

i haven't tested this myself, so i'm just guessing. I've been doing 3D since about '82, but as an XSI noob, I could be full of it.

09 September 2004, 10:19 PM
pretty weird never noticed that.... I did a test myself and preview images are indeed smaller (in Mb). My first guess of why the smaller size was that previews did not save an alpha channel, but both RENDER and PREVIEW images do have an alpha (I tested it). Antialiasing would affect the quality of the image but not the size, it would just affect the staircased borders so the change in image size would be minimum. My guess is that the preview images are compressed but checking both the look pretty much the same, so if it is compression I guess the compression is in softimage pic's style they don't compress color but they ignore pixels with no geometry ( plain black).

09 September 2004, 11:09 PM
According to the image information dialogue of PaintShopPro, images produced by the preview renderer use "run length" compression, while those straight from the renderer use none.

09 September 2004, 11:48 PM
ah, so my second guess was correct.

at least RLE is lossless, so all other things being equal, the image quality will be the same. However, I can't find a place in the render settings to turn this option on or off.

too bad, because it would be nice to be able to do final renders of compressed TGAs.

Anybody know where this setting might exist in the UI?

09 September 2004, 03:53 PM
too bad, because it would be nice to be able to do final renders of compressed TGAs.

Anybody know where this setting might exist in the UI?
Yeap I totally agree with you, it would be cool, that's why I always render in softimage pic format since compression is lossless and file sizes tend to be smaller, but my guess is that we don't have access to compression of tga files at least not in the UI, it's a shame.Even the export option of the flipbook has no parameters for compression of tga files.

09 September 2004, 09:24 AM
I tend to go for PIC as well, works great with all avid products and if you have a small plugin you can open them in PS as well, most other comp apps should read them fine. If you need 16 bit go for SGI. Thats what most places seems to use, probably because flame/inferno etc has such good support for that file format. It also works great in shake.

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