Grass - I need a displacement multi. of 30 to notice a change - normal?

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Just like the title says:

A grass vismat I am using I have had trouble with trying to achieve a noticeable result with 3 or 4 on the displacement multiplier. So I tried 30 for the multiplier to make sure SOMETHING was happening. It has been rendering for quite a while (40 minutes or so +) is this normal by any means?

It worked so I guess that’s good, but the Vray for Sketchup manual shows that tutorial for displacement and mentions that a multiplier of 2 would yield results.

Confused.

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Re: Grass - I need a displacement multi. of 30 to notice a change - normal?

Displacement deform geometry, so vray need to calculate that, and the rendering time will grow. Displacement it’s very difficult for me, so I can’t give you more info about it. I know that you should have the surface (where you want displacement)grouped.So select the surface with all the edges, make group, then apply displacement.

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Re: Grass - I need a displacement multi. of 30 to notice a change - normal?

Multipliers are dependent on the scale of your scene. If you have your scene units in mm, then a multiplier might need to be much larger than if you had your scene units in feet. Displacement does take longer to render, since V-Ray has to calculate the displaced mesh. SU geometry is notorious for being harder (and therefore slower) for us to get access to. Also doing fine displacment on very large faces will take longer than if that face were divided in to somewhat smaller faces.

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Re: Grass - I need a displacement multi. of 30 to notice a change - normal?

. . .OR

You could try Micha’s grass technique, used by some forum members (including me)
http://asgvis.com/index.php?option=com_smf&Itemid=90&topic=2320.msg18834#msg18834

I think it gives very good, and of course, realistic results.

David

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Re: Grass - I need a displacement multi. of 30 to notice a change - normal?

Do I need to resize the picture when I apply it to the environment? and how. Is it like applying vismat?

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Re: Grass - I need a displacement multi. of 30 to notice a change - normal?

When you change the texture type to ‘environnment’ you are selecting how many repeats in a circle - hence the 9 in the horizontal repeats box.
You apply a grass texture in SU and set up the linked material (in Pre SR! version) as shown. In SR1 the material is set up for you so you just go in and change the diffuse layer in the Vray material editor.
So, yes, it is like applying a vismat.

473×594 37.7 KB

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Re: Grass - I need a displacement multi. of 30 to notice a change - normal?

So if I input higher values on the repetition, the smaller the image gets? Is this the way to control the image size because i have some trouble matching the grass size with the scene. Is that correect?

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Re: Grass - I need a displacement multi. of 30 to notice a change - normal?

JudgeBao
I think that is correct, but at a certain point more repeats also starts to distort the image you are using. This is probably not critical with grass, but would be if the image was a building. Thats one of the reasons why I use billboards for building reflections - you get more control.

David

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Re: Grass - I need a displacement multi. of 30 to notice a change - normal?

JudgeBao,
Make sure that your camera hight is at human eye level. This method great for ground covers, but it works only from human point of view.

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Re: Grass - I need a displacement multi. of 30 to notice a change - normal?

Hey 40th, did u use it in your current building, I think your grass is absolutely wonderful. I cant use displacement grass because it eats a lot of my rendering time. So i want my grass to look nice even not to apply displacement

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thanks for ur trick…
can i have jpf of that grass map
thanks..

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thanks for ur trick…
can i have jpg of that grass map
thanks..