Help on EZ topic. =)

PrancingJenny

I'm sure this is EZ for many of you, but I'm stuck on something bizarre.
In max 2010, I've created a plane object , put 3 grass shaped scatter objects on it to create a simulated grassy feild.



Problem is, when I put a light in , it seems to caste darkness over the feild, instead of actual light. I'm so confused. Maybe someone here knows what I'm doing wrong. Here's the image of this strange darkness appearing when the light is added to scene.



Thanks for any help on this.

cw

show me the properties on your light plx.

PrancingJenny

I re-rendered the scene with only two grass scatter objects, but the lighting effect is the same. I've tried it many times but the light is always casting this blackness.


Here is the light properties:


Thanks for any help.

PrancingJenny

Another attempt with some plant scatter objects but the light does not seem to work properly..

cw

very peculiar

nothing funky with that object is there? the grass blade? also, can u try a different type of light, and the basic max scanline renderer.

ta

aniceto

its obviously not a cast shadow since shadows are turned off in the light. so kinda looks like it could be a problem with the grass normals maybe. I cant tell from the screen grabs, but maybe your grass blade object doesn't have enough sides?

Rick Stirling

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Stupid: HELP ME!!

Smart: Help required with getting model into UT

Smarter: UT model exporting issues - model is wrong size.

PrancingJenny

My apologies for the dumb sounding thread title - next time I'll be more descriptive.

Here are more images of this bizarre rendering anomaly. Here's two scenes, I took a standard AEC plant object scattered over the PLANE object. Just a simple process, add the light and still , notice how it casts blackness over the scatter object.

Eric Chadwick

Well these last two renders do look correct. You're using an Omni, which is a point light so the light comes from one point in space. The backsides of your meshes will be black if there's no other light.

In the top shot, the meshes look like inverted cones, so they'll be black on the far side. The bottom shot looks similar.

For the original problem, have you tried Reset Xform? Also have you scaled the light or the camera in any way?

PrancingJenny

I tried to use the Reset Xform and Collapse technique but with the same results.

Here's another attempt, a single grass shaped poly object applied as a scatter object onto the plane.

It renders fine but when I put in a light (omni, or spot, with default settings) it castes this bizarre blackness over the scatter object.



The omni in the scene is positioned directly in the center of the plane, so I assume it should light up the center but in this case it just shooting light onto half the plane and black on the other half.

It seems nobody who seen this has encountered the problem yet - may I ask, does anyone else here use the scatter technique to simulate a grass terrain?
Is there a better method then this that I should be using?

I really appreciate any input, thank you!

Eric Chadwick

Ah, I think this is because you're using flat single-sided meshes for the grass stems. Either put a shell modifier on it, or better still feed it a 2-sided mesh (not just disable backface-culling).

PrancingJenny

This took me awhile to figure out, turns out it's all in the lighting.

After adding 1 Target Directional light (shadows ON) and 4 Omni's (shadows OFF) on all sides of the field, the lighting remains consistent from all sides with no black anomalies.


Thanks x1000 to all who helped me on this!! :thumbup:

Also learned about the shell modifier and ResetXform / Collapse technique. Thank you!

aniceto

maybe your grass blade object doesn't have enough sides?

I think this is because you're using flat single-sided meshes for the grass stems.

its not your lighting that's the problem.

Mark Dygert

Did you mirror the grass?

PrancingJenny

@Vig: I didn't mirror the grass.
The grass is just a single triangular shape made from 2d splines (converted to poly> bend modifier to 60 degree> collapse all) with a 2 sided green material applied. The grass object is then applied as a scatter object over the plane.
When you add the light this black patch appears as the pictures above show. But I've managed to get that under control with adding a Target Directional and some well placed Omnis, and it appears to work.

@aniceto:
Darn I was really hoping the lighting was the issue.
My grass blade has only 1 side, a 2 dimensional object... but I tried using one version with the Shell modifier to thicken it up and had same problem. I tried using a full 4 sided box mesh as the grass blade and that two had the problem (I believe).
The only luck I've had eliminating the black spot in the field was by adding that Target Directional and 4 omnis. Seemed to work but if you know the real problem I'd love to know, and finally put this to mystery to rest.

aniceto

you shouldn't have to solve it by using 4 lights. maybe you could post the scene file? cause I really cant see it being an issue with the lights, and if its not the mesh itself then I'm kinda curious to know what actually is causing it heh.

PrancingJenny

Here's the link to the scene file:
http://rapidshare.com/files/385893441/Grass_project.max.html

I included a grass object called "Sample" in the scene, made exactly like the one scattered on the plane, so you can see how its made.
btw: very grateful for your help.

aniceto

its definitely the 2d mesh. I deleted the 4 omnis and set the main light higher then added a shell to the scatter object and rendered from a few different angles and it worked out fine. the only darkness i got was cause there's no fill light or GI, nothing out of the ordinary.... ๏̯͡๏
I'm not sure why you had a problem with the shell not fixing the issue, unless you just rendered from one angle and only saw the dark side of the grass objects?

PrancingJenny

I cannot thank you enough aniceto!!

I did exactly what you did, and IT WORKED!!! Don't know what I missed when trying the shell technique the first time, but YES, following your simple steps solved the problem from all angles.

I wasn't aware of GI so I'm spending time now to investigate and apply it to the scene. (gonna look into fill lights too).

Eric Chadwick

Yeah I also got the same lighting when I made the grass from scratch. Plane with a couple segments, Taper mod, Bend mod, Scatter compound object, and choose a ground plane.

It went away when I started with a 3-sided Cylinder instead of a Plane, or when I used Shell on the Scatter object.

renderhjs

you might want to look into the hair and fur modifier instead of the scatter object as it is much more powerfull and recent as the prehistoric scatter object in max.
Even with the HF modifier you can instantiate custom poly or mesh nodes - but with greater control.

PrancingJenny

The Fur and Hair idea produces nice results, maybe I'll use this instead of the scatter technique. (Fur seems to be easier with more options)
Here's a render using Hair and Fur on a plane, with one target directional light overhead (no shadows):


However when I Enable shadows on the overhead light, all the Fur/grass turns black like so:



If anyone wants to look at the file and see if they can figure out why the Fur turns black in the light, Here's the link:
http://rapidshare.com/files/386063577/furgrass2.jpg.html

Mark Dygert

Delete the light and put a new one in. When you add hair/fur it should add some parameters to your existing lights but sometimes it fails to do it. You can add it manually to your lights by going into Rendering > Effects in this case with such a simple light set up, just recreate it.


Also set the light to shadow map instead of ray traced. I think you'll have to set the hair/fur to render as geometry before you can ray trace. also ray tracing with that much geometry is going to kill render times, might as well go with a nice quick fuzzy shadow map.

You might want to kill the opacity setting for the tips, that's great for getting a fuzzy look but not so great for grass. Also toss in some kink and frizz. The great thing about doing it this way is that you can have it effected by dynamics now like gravity, wind and collision objects.

PrancingJenny

Many, many thanks Vic and all else who helped me through these mind bending light issues, and gave me all the extra tips!