Using a bitmap as dirt and scaling it

[OzBoz]

Since fernando made a great tutorial on how to use 'dirt' in your renders I wanted to try some stuff. But what I don't get.. if you use a certain bitmap as 'dirt' how can you change it's scale to prevent it from repeating.

Maybe I look at all the wrong places but I don't find the answer.

[probitas]

Re: Using a bitmap as dirt and scaling it

i have the same issue - when using a bitmap for the 'white' of a dirt texture, the image does not register in SU, thus there is no way to control how it is mapped on a surface...

[dkendig]

Re: Using a bitmap as dirt and scaling it

you have to do a little hack to map stuff in SU if you don't have a texture in the diffuse layer. Basically you just need to make another diffuse layer for the material, and make this new diffuse layer the topmost diffuse layer (that is the diffuse layer that is used for the SU material). Use a bitmap texture of some sort in this layer. Adjust the texture in your SU viewport until you're happy with the way your texture is situated on the object the material has been applied to. Then when you're ready to render, turn the transparency of the topmost diffuse layer all the way up (don't remove the layer, just make it invisible). Now when you render, you will see the material will show up fine with the texture mapped properly.

So why do you need to do this? Because SketchUp simply will not allow an object in a scene to have UV mapping, unless a texture is being used. To add to the fun, we don't set any texture for the SU material unless you are setting a texture in the topmost diffuse layer of the material. So this workaround is necessary if you want to apply a bump/displacement map, or any map for that matter, unless you have a texture already set in the topmost diffuse layer.

[OzBoz]

Re: Using a bitmap as dirt and scaling it

Thanks dkendig! Helps a lot also with other maps like bump mapping etc. without changing the basic diffuse map.

Maybe it's a good idea to collect more of this kind of 'things you want to know' and put them in a separate chapter in the manual. For example, I was sometimes annoyed by the sharp shadows of the sun. Increasing the sun size did the trick but so hard to find out.

So instead of reviewing all options you start with a problem like 'why does my image have so much stains/spots/dots in dark area's and then just some settings which will cause/solve it most of the time.

Just an idea, but you can ask the community to bring their nice 'things which are useful to know' in a topic. Bet lots of users have nice tips for others.

[probitas]

Re: Using a bitmap as dirt and scaling it

thanks devin. works great!

[dkendig]

Re: Using a bitmap as dirt and scaling it

OzBoz - great minds think alike Feel free to copy and paste anything from this thread, in to that one, that you feel would be useful for our manual. Also feel free to post anything you can possibly think of that we should try to put in the manual. Or... don't, and we'll do the best we can to cover anything we have information about.

I'm glad I could help you guys out though Such an annoying workflow issue!!!

[inbalto]

Re: Using a bitmap as dirt and scaling it

Im having trubble with the dirt also-

Can someone please refer me to the link of Fernando?

My problem is that I how to use the ditr on a texture?

I have a brick texture, so it I put the dirt on that texture, it replaces the texture itself.
If I make another diffuse layer and have the dirt on it, I have to make the first layer transparent, but then I see a white background: the background of the white dirt layer.

I tried having the dirt transparent and bring it above the brick layer but it won't render good also.

What am I doing wrong??

[probitas]

Re: Using a bitmap as dirt and scaling it

1. make your textured material in sketchup as usual.
2. position the texture in sketchup so it looks how you want.
3. open vray material editor, select this material
4. add a diffuse layer (it should appear below the original as "Diffuse1")
5. in the new diffuse layer, add a dirt map in the map slot
6. under "white_color" in the the texDirt menu, add a texBitmap - this is the exact same diffuse map that you originally used for the material.
7. before rendering, make the original diffuse layer ("Diffuse") completely transparent, ie. transparency color should be pure white.

if dirt still isn't showing up right, try to adjust the 'radius' parameter in the texDirt menu to increase its spread.