What causes artifacts in this render?

Started by daudvyd, August 15, 2018, 07:52:58 pm

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daudvyd

I'd appreciate some expert advice (or more expert than me!) Please see the annotated attached render. I have questions about the parts of the image marked with a letter:

A) These two terrain peaks have an odd white mist or glow near the top. I don't think it is caused by the light source. What else could cause it?

B) There are white specks in the foreground of the image. They look like "hot pixels" or tiny reflective stones. What could cause this?

C) The clouds appear to circle this terrain peak appear. I believe this occurred just by chance. Is there any node arrangement that would allow the terrain peaks to affect the clouds?

C) Another question about the sky--how can I render the sky on a separate layer from the terrain?

bobbystahr

A. maybe your Haze setting in Atmosphere?
B. possibly tearing mesh from displacement? Can you adjust the displacement tolerance on that layer anywhere, if so up that; also when I had a similar problem I increased the patch size in the Compute Terrain.
C. see attachment.
D. depends on which version you have, the pro has Layers.
something borrowed,
something Blue.
Ring out the Old.
Bring in the New
Bobby Stahr, Paracosmologist

WAS

Quote from: bobbystahr on August 15, 2018, 08:40:57 pm
C. see attachment.


This feature seems to be a bit of a hit or miss right now. I get the best results using a Displacement to Scalar and Colour Adjust to "Define" the terrain how I'd want it to effect the clouds, than I pipe that colour adjust into the cloud altitude and use it's function multiplier. Also good to note the terrain must have it's low and high colours (or at least high colours).

You may also be able to fool layers by rendering a scene with atmosphere, and than render a scene without render, and with the background objects background changed to a solid colour to replace, such as a solid blue or green. Haven't tried. But that would give you a mask which you can than replace with transparency in post. Than you can render a scene with no terrain, and only atmosphere and clouds and do your final compositing.

daudvyd

Thanks bobbystahr & WASasquatch. I'll try those possible solutions!

bobbystahr

Quote from: daudvyd on August 16, 2018, 08:02:13 am
Thanks bobbystahr & WASasquatch. I'll try those possible solutions!


cool, let us know what works
something borrowed,
something Blue.
Ring out the Old.
Bring in the New
Bobby Stahr, Paracosmologist

Oshyan

A: that is probably atmosphere affecting the terrain, as Bobby suggested. The question I'd have is what the scale of your scene is, how tall those mountains are. Most units of distance/scale are in Meters in Terragen. It's possible you just have some very tall and/or far away mountains, which means they're more affected by atmospheric haze. Or you may have increased the Haze, causing this effect.

B: I would guess that's not exactly "tearing" as Bobby put it, the color is wrong for one thing (when tearing occurs, you see the sky through the missing parts of the terrain). However, it does appear that you have quite strong, spiky displacement on the ground, so it's possible. In that case I'd suggest reducing the roughness and/or displacement amplitude of your shader(s) on the terrain. That being said I think it may be more likely to be reflection, are you using any on any of your shaders? If so just reduce or eliminate it.

D: Terragen Professional has a render elements/layers system that lets you separately output the sky and terrain, among other things. See documentation here: http://planetside.co.uk/wiki/index.php?title=Render_Layers_and_Render_Elements

- Oshyan