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Tree material too bright compared to original dark material

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Re: Tree material too bright compared to original dark mater

Unread postby esmith » Thu Sep 19, 2019 6:45 pm

Hey mate, not sure what you are totally trying to do here. It looks like you want to do some look dev on a speed tree, and because you are using a shadow caster I'm assuming that you want to render it on top of some plate. To do that you need a few things, so follow me and I'm sure it will all make sense.

Speedtree and no lights, in progressive rendering mode = should be black, and is:
Capture.JPG


Ok now lets bring in a light. You used a simple single color environment light. In my example I'll use an HDRI and I'll make sure that the Environment light that's using the HDRI is set to display and render the actual HDRI image as a backdrop as well.
So as you can see, we have the background, and in fact our tree is being correctly lit by the HDRI Environment light
Capture.JPG


Now lets make a polygon floor under the tree to catch the shadow. I rotated the camera just....cuz I wanted to see other trees.
Capture1.JPG


NOW, lets add the shadow catcher material with all it's defaults. Again as expected but not what we want
Capture2.JPG


The first thing we need to do is set the Opacity Mode to transparent.
Capture3.JPG


And in fact that may look like we are done. But if you look at the options for the Shadow Catcher there are few more things we should concern ourselves with, namely THE EMMISION COLOR. Why? Because in order to catch the shadow of the tree, we've had to put a piece of geometry under the tree, which of course is now blocking the light from the HDRI!!! Why? Because we are in a ray traced world, and geometry casts shadows, in this case a shadow up onto the tree from the bottom due to the light from the bottom side of the HDRI being occluded.

So by using the emission color attribute, we can simulate the bounced light off the road. In this example, I've made it bright red, so you can easily see how it's working.
Capture4.JPG


So the PROPER way to set that up, is to map the the emission color with a camera map of the same image being used by the Environment light. But in this case, all we need to do is approximate the color of the road in the setting
Capture5.JPG


And VOILA....we have a tree integrated into the plate!

Here is another render, showing your initial problem. And that is just having a default'ish shadow catching material casting way to much bounced light up from the surface
Capture6.JPG


I hope this helps
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