Growing grass…


I just said I will let the grass be for a while but I can’t help myself. I try to finish my scene but I only get grass related new ideas. This comes from not doing a project on a schedule!

cat in grass

My goal is to make a better looking grass but render it fast and be able to reuse it in other projects easily. Now I have 500 000 particles in my scene. Blender handles it well, render time is acceptable and the result looks well at the point the grass meets objects, you can see it’s not just an image mapped on a plane, but close up you can also see it’s too scarce. At first it seems that only the increase in the particles number will give a realistic result, but this makes Blender get stuck (even when I set the particles not to show in viewport!) and render time go up, so this won’t do. I’ll have to mix a minimum particles scheme with a better map on the object that shows underneath the particles grass so it camouflages the problem.

In a separate file I made a plane with my particles grass, so as to fill the viewport; kept all the light settings from the original scene,  so the grass map and the 3d grass look the same; disabled received shadows from the material under the 3d particles, set a high enough number on the particles emitter and went to the kitchen to get Eva’s breakfast ready (also using a blender) until a nice field of grass was rendered:

grass field-viewmap-mic

The new bright idea I had now was to use the “view” mapping on my ground object, so this will map my grass field independently from camera angle:

10mai-iarba verde-viewmap

I now have grass in correct perspective, something I could use anytime. I could also try and make a nice grass lawn from photographed grass and use it this way.

This works only for still renders, in animation you would see the texture behaving oddly.

Next I add the 3d grass on top. I think making the particles not to cast shadow on the surface beneath would have been even better but I was not able to do this. Unfortunately Blender does not have the option to disable an object from casting shadows. You have some workarounds like making another object not to receive shadows or setting the sun not to cast shadows on particular layers but I can’t get them to work in my scene. If I disable shadows from my ground object, it will not receive shadows from the particles nor from anything else so I won’t get much shadow under the deck. Same with the sun shadow setting, grass won’t cast shadows but neither it will receive, making the area under the deck look bad:

10mai-iarba verde01-eroare1

There might still be something to do about it using render layers but I don’t have time to test it now. Leaving it for later, keeping the particles shadows for now.

…stuck again… after messing with various settings to get rid of the shadows I can’t get them back on.. argh…

..ok it was a shadeless material on a grass blade!

Final grass result:

10mai-iarba verde06

I think it’s the best result I got so far. The grass might look a bit large scaled but I’ll leave it like this for now. Next to arrange the trees and make some tidy final renderings.

For the 3d particles grass I used the method in this tutorial: how-to-create-realistic-grass-in-blender.

There is another older tutorial from Andrew Price here,  should be very good only it uses Blender 2.49 so I’ll better wait for his updated Nature series.

Happy blending!

Categories : Blender stuff