advanced rendering for AutoCAD
I'm working on a project where I am rending a shade structure that I want to composite onto a site photo. I've set a ground plane and tagged it as alpha channel, but what I get isn't how I think it should look. I'm not getting any transparency in the shadow (well, just a tad maybe).
I've done this in the past and I think all my settings are about the same. What am I doing wrong??
Samples: (Click to enlarge)
Image while rending. I think the items tagged as alpha used to show here, but I cant remember for sure.
Compositing in photoshop... ick!
Composite using render on ground plane not tagged and using sky alpha, masking using materials channel, and masking just around the shadow. Desired look with a lot more work to get it.
Sahara table. Brand-new stuff from Sven Christiansen Peter? :D
Nice paradigm with explanation. Thanks.
I did try using a material similar to the photo I was matching, but not with the background, as Peter suggested. I'll give that a go. I also used a solid background, but should have gone darker as you suggested, not lighter.
That one worked as is because you're compositing with white.
The visible background you use while rendering is not relevant-- other than it may effect the exposure of the image-- which can be reset using the Brightness setting. (Reflective backgrounds may be important-- depends on the image.) (Peter is probably right in that it's easier to adjust things if you see everything at the same time.)
When compositing you have complete control. You can save off as many mask channels as you want in the image editor and edit them independently. You decide what colors to combine using photoshop, not the rendering background. The renderer encodes how much occlusion there is into the alpha channel when creating those shadows-- it's just a guess though (there is no way to really do this)-- and you may need to adjust the shadow portion of the mask channel.
If you want to include the nXtImage of the thing I can take a run at it.