The effect of the object on the stage without the object itself
valieravaliera94
Posts: 0
Hello! Tell me, please, how to make a character cast a shadow on the environment (or any other interaction of the object with location) WITHOUT the character drawing itself? My machine does not allow me a good rendering of a character and location. Therefore, I want to render the location in very high resolution and then downscale it to a lower one and use denoise in PS if necessary.
Thanks!
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In Iray you can't; in 3Delight you could use pwCatch (applied to the thing you don't want to see and set to background), though I'm not sure it would save memory.
One common Iray trick requires two renders. Note: both renders should be the same pixel size.
First, render your character(s) only. Hide any other objects in the scene except your lights, and set Render Settings>Environment>Draw Dome and >DrawGround to OFF. If your environment is your lighting, it will still light the scene. But it won't appear in your render. You'll get a render with your characters floating in a transparent background. That's what you want.
Next, render your background. Because you want shadows from your characters, use Edit>Duplicate Node Hierarchies to create a copy of each character and name it something like Name_Shadow_Only. Then hide the original characters. Create any primitive, set it to Iray Uber Base, and save a Shader Preset called Iray Base Zero. (This is a good shader preset to have anyway.) Set all of the Shadow_Only characters' Material Zones to Iray Base Zero, change the Base Color to black, and Glossy Reflectivity to 0. That will make your Shadow_Only characters matte black. (It will also remove all of their maps, so your background render will need less memory). Render the background and your matte black characters will be casting shadows.
Finally, in PS or GIMP or whatever image manipulation software you use, load the background render in your base layer and load the character render in a new layer above the base. That will superimpose your characters over their matte black Shadow-Only counterparts, with their cast shadows still there.
Here's what I do (using Iray preview mode):
Once you have your character or whatever selected, go to Scripts>Utilities in the Content library. Select the Create Advanced Iray Node Properties button. Then go to the Parameters tab for the object and turn on Enable Iray Matte. You can select multiple objects and turn them all on at once.
Next turn the item visiblity off, then back on. Now it'll have a weird partially visible look to it.
For the last step, select the objects you want to make invisible, then go to the surfaces tab and select all the surfaces. You can select the top one and Shift+Click the bottom one and they should all be selected. I usually set all surfaces to Iray Uber, I don't know if it's necessary, but it makes them easier to edit. Once you have them all selected, look for the opacity control and set it to zero and you should be done!
I don't know if this is a feature in Iray or a bug, so it may be removed in future updates. But for now, it's pretty useful. I don't know if it will save you any memory when rendering since Iray is still loading the object even though it's invisible.
That's bloody brilliant! Does it work when you click render, or only for the preview mode?
If it is a bug, I hope they leave it and make it a feature!
It works in preview mode and render mode for me. I stumbled on it by accident when I was working on something else.