Scaling Edge lenght proportionally to resolution.

[Matt_GF]

Hi guys.

I have a question about modifying the value of edge lenght in VRayDispMod according to the resolution of the render.

Let's say that I have a a scene 100x100px and set the Edge Lenght to 1px. Then I render the scene in 300x300px resolution. Should I multiply the edge lenght by 3 or by 9? The area of pixel in 100x100px res will take 9 pixels ( 3 x 3 ) in 300x300px res.

[hermit.crab]

The 'Edge length' parameter of the VRayDisplacementMod is the maximum length in pixels (or world units if the 'View-dependent' option is turned off) of a sub-triangle edge after the subdivision prior to displacement. This means that scaling the 'Edge length' with respect to the resolution (like in your example) would result in an equivalent level of displacement quality (in terms of subdivisions) between renderings, however, that would not necessarily produce satisfying results (displacement may look too jaggedy in the higher res render). One should choose the 'Edge length' amount depending on the desired quality of the displacement with regard to the rendering time, rather than calculating an exact amount.

You can read more about the 'Edge length' parameter in the technical documentation here:
https://docs.chaosgroup.com/display/...ng/Subdivision

[Matt_GF]

Hi Aleksandar.

Thank you for response.

"This means that scaling the 'Edge length' with respect to the resolution (like in your example) would result in an equivalent level of displacement quality (in terms of subdivisions) between renderings"

that was exactly what I meant in my question In terms of subdivisions, should I assume that it would be 3 or 9 times longer edge lenght, I was concerned exactly about that part.

When it comes to the look I can modify it then to get the look I want but I was just curious only about the "mechanical\subdivisions" part this time.

So, in this particular example ( 100x100px to 300x300x ) is it x3 or x9? I would be very grateful for answer for this question. I checked the documentation for Mac and V-Ray 3.6 and 4.x and couldn't find answer to this question.

[dgruwier]

If you're in a hurry, you could just do an experiment. Render a mesh with wireframe in two different resolutions, one with 3 and one with 9 times longer length, compare the results.
If you do the experiment, please post the results, I'd be curious too. I've used 3 in the past.

[hermit.crab]

To match the 100x100px resolution's edge length of 1px to the 300x300px you must use the same multiplier as the resolution resulting in a edge length of 3px. To match an edge length of 3px in an image of 500x500px to an image of 2500x2500px would be to multiply 3px times 5 equaling an edge length of 15px.

[Matt_GF]

I will trust Vlado on this one. Thank you Vlado for answer.