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Realistic Grass Rendering on a Site model


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pls can anyone help me with realistic grass rendering on a quite large site model (approx. 100 x 200m)...once I place texture bed on a site model and change texture bed class details texture to grass shader, the final render is without realistic grass


When I do the same process with smaller site model, it works


Any advide please


Im using Vectorworks 2020


Thank you

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I think the problem is that the top polygons of a VW DTM are flipped.

So the grass grows downwards into the terrain ..... so you just can't see.

I thought that was fixed in any way some time ago ?

At least that was a thing on the german forum.


4 hours ago, martin.vacek said:

the final render is without realistic grass


Yes, we could argue to which degree VW grass shader is realistic



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@martin.vacek The method and texture used will depend on how close you want view the grass.  If it's an aerial view of a large site, I like to make textures from actual aerial photographs that show variation in the grass surface and not tile.  If you are intending on doing close up eye level perspectives, a different texture is generally needed that has a different level of detail.  Maybe post a few images of what you are intending to accomplish to get better advice?


Check these out for some ideas...





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@jeff prince Thank you very much for answer, pls see just simple Site model with texture bed on, lets say 200 x 100 meters large and in open gl (1) version and render version (2)

there should be blades of grass with height 0.5 meter with good density as in the grass shader


i did the same process with just small piece of Site model (4 x 4 meters) and it works (3 + 4)


thank you in advance





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18 minutes ago, martin.vacek said:

@jeff prince Thank you very much for answer, pls see just simple Site model with texture bed on, lets say 200 x 100 meters large and in open gl (1) version and render version (2)

there should be blades of grass with height 0.5 meter with good density as in the grass shader


i did the same process with just small piece of Site model (4 x 4 meters) and it works (3 + 4)


thank you in advance





I think what you’re seeing (or not seeing) could be related to the bug described in the following old thread, where displacement mapped textures (like the Grass shader) show differently based on the size of the applied object.


Also described in this thread:


Edited by rDesign
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To follow on Jeff Prince’s comment, here’s a suggestion from @Dave Donley to use the ‘parallax mapping’ (found in the Bump shader parameters) instead of the Grass shader:

From the Vw2020 User Manual:


Parallax Offset (%)

Sets the amplitude of the parallax mapping. Positive and negative values can be entered.


Parallax mapping enhances bump mapping by giving textures such as bricks more apparent depth, without the performance slowdown that can be associated with displacement mapping. Unlike displacement mapping, parallax mapping appears flat in silhouette.


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@martin.vacek It depends on what your final views end up being.  Personally, I prefer to use simple non-bump materials for everything and then sparingly use bump materials for things very close to the camera, if at all.  Also, you could cut your site model up into several pieces to allow for using highly detailed textures in only the exact areas you need.  This may help get around the grass shader 'size of object' issue mentioned in the earlier linked threads.  Probably the best way is to handle the really detailed foreground areas in post with a photo editor 🙂

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@martin.vacek so your problem got my curiosity going...  Using a texture bed failed as it grew the grass downward.  Thought that it may be due to the direction the texture bed polygon had been drawn, so I reversed it.  Same failure.  Redrew the correct way, failure.  Hmmm.


So, I used the multiple site model trick that helps with all kinds of challenges.


Here's what I did in this case....

Made a quickie site that is roughly 700'x500'

Duplicated the site model in place.

Created a curvilinear shape to develop an area to use a grass shader on that would sit on one of the hill tops

Used the shape as the site model crop for the duplicated site model.

Applied the grass displacement shader to the cropped site model on the hill top, applied an aerial texture copied from a stock photo website to the larger site model.

Render with custom settings, turn on the grass shader.

Admittedly, the aerial texture I used in this example is poor, but I didn't spend any time trying to source one that would compliment the grass shader.  Once trick that is kind of handy for creating matched textures... make a rectangular extrude and apply the grass shader to it, render a top view with the same lighting settings used in your model.  Boom, you now have a 2D texture map that can be made into a texture that will match your intent with the grass shader for distant views.  I should have thought about that before typing this post 🙂


Alternatively, just use 2D textures in Vectorworks and do your fancy renderings in TwinMotion, which has nice 3D grass that renders quickly.

hope it helps.




3d grass on little site model, black area is the big site model.




Random stock aerial photo off google applied to large site model, grass shader on the little site model.  No site modifiers or texture beds used.






grass shader applied to rectangle, rendered from top view.  at least keeps things in a similar color family.  Could spice it up in photoshop using some filters and such.




replaced aerial texture with the one above in this image.  Could be done better with more time and effort.




Edited by jeff prince
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On 2/27/2021 at 11:04 PM, jeff prince said:

@martin.vacek I'm curious why you want to use that grass shader over such a vast distance, the render time will be killer.



I experienced that yesteray by accident when I opened an old project for testing.


At first, when I saw GI calculation going on and on I was shocked that my

M1 Mac Mini is terribly slow for RW Rendering.

It was an easy scene and I thought it had been much faster even on the old

Trash Can Mac Pro.

So I canceled and went to Windows Ryzen 3950X and it was similar slow.

So I let it alone for Rendering and after 12 minutes I realized that  activated

Grass Shader Rendering. But it was only a small area around the House.


Tried a bit more to optimize it for render time with decreasing density.

But everything below what I already had didn't look like Grass anymore.

So I deactivated Grass rendering and had my usual RW responsiveness.

Sub 1 minute for a screen rendering in the Ryzen case.


Went back to M1 Mini and tried again without Grass Rendering.

And it was about 1:30 Minutes on my M1 Mini.

So about 66% of astonishing render power of a 16 core 32 thread Ryzen !


Surprise, now I am even more happy about my M1 Mini for VW RW Rendering.

And will avoid Grass Shader in VW or C4D.

AFAIK GrassShaders works much better with Modo or Vray.

Edited by zoomer
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@zoomer I'm lucky that openGL renderings satisfy the majority of my needs.  I've done a lot of fun playing around with bump maps and grass shaders, but the render time requirements just make it unrealistic for most of my needs.  Cool though 🙂


Here are some of the bump map test I was playing with last year.  Ramping the faces of stone so they were not in the same plane.  Fun for super close up work, pointless for distant views.




same texture without bump


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This is a bit sideways pertaining to the grass topic, but if any of you use c4d, there is a fabulous plugin called 'Grass Kit' that is pretty incredible.

Instant grass of all sorts, lengths, density, include wildflowers, landscape rocks etc, etc.

I won't prattle on, but it may be of value if you do use c4d.

Here is a link if you are interested. 



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