Making 50% transparency trees with RPTreeMaker

Hi,

I've been using Sketchup for half a year now and just starting to know my way around. I have Irender for the second week now but was already sold when trying the trial version.

What I'm trying to do is render a scene from the outside. Things seems to be getting to the way I want them to be except from the trees. Since i'm having a row of trees in front of the main building, and I want to see it and not the trees, I want to make them 50% to 70% transparent. Thing is, I've tried messing with the irender material editor and the Sketchup Material editor and can't seem to make them transparent at all.

The only way I can see is render the scene without the trees, and after that re-render it with the trees, then get everything on photoshop and get the layer with the trees to be 50% opacity but it's a real pain and really time consuming.

Any help would be appretiated.

Thanks.

Simon Loisel-Goudreau

▶ Reply to This

Replies to This Discussion

Permalink Reply by Render Plus on March 3, 2011 at 4:24pm

Are you using nXt or RPTreeMaker trees?

If you have an image of trees, you should be able to make the .PNG file of the image transparent in a paint program (which allows partial transparency) and they should work. I'll have to try this later -assuming I can find a paint program which does this - (or maybe I can find a partially transparent image on the internet).

The transparency in IRender nXt should also have worked - placing an image of a tree on a face, and then marking it as transparent. However in this case you also need to set the Index of Refraction to 1.0 to make sure that the trees are not treated as reflective glass. I'll have to try this later as well.

If you are using RpTreeMaker trees, then you will need to render the trees separately, save the rendering as a transparent .PNG image and then place the image in front of the drawing.

Also, there is a Foreground tab on the setup dialog. You should be able to us an image of trees as a foreground image - and use the blend slide to make them transparent.

▶ Reply

Permalink Reply by Render Plus on March 3, 2011 at 5:35pm

I tried using the Foreground Image. I think is is probably the best solution:

Transparent Foreground Trees

We want to place some trees in the foreground, but make them transparent to the rendered scene is visible behind the trees.

Rendered image with transparent foreground trees.
(Using Multiply Mode - where trees make rendered image darker where they intersect.)

Place some trees in an empty model (or on a layer, so you can turn off all other layers) and render them.

Rendered Foreground trees

Save the rendering as an alpha PNG image - the sky and ground will be trimmed from the image.
Using the Foreground Setup Tab, select the saved tree image as a foreground.
- Be sure to turn of masking (which causes the image to only be placed over actual geometry)
- Try with and without Multiply Mode to find the effect which you like best.)

Foreground settings

Render the image

Rendered image with transparent foreground trees.
(Without multiply mode - trees are blended in with the rendered image.)

The foreground image in front is only going to work if you don't want other objects - such as the people - in front of the transparent image. What is nice about the transparent foreground is that you can adjust the transparency without re-rendering - especially since Rich fixed the Apply button yesterday.

If we could make the trees transparent, it would be done on a object by object basis, and probably wouldn't work well because where there was a single leaf you would get the transparency you want, but then two leaves intersected, or leaves intersected with the trunk, you would get more obstruction because transparency is applied to each object one at a time.

Here is a rendering of a single transparent leaf in front of a house on the left, and 8 overlapping leaves on the right. You can see through the leaf on the left, but not through the multiple leave on the right.

To get the effect you want, you want the whole tree to be transparent as a single image, as in the image below. Note that I have place the bench and fence in front of the transparent trees.

If the trees are not overlapping, this is easy to do:

1. Place a RpTreeMaker tree - but set its image quality to 'high' or better when you create it.

2. Place the tree into SketchUp.

3. You want to use the tree as an image, and not re-render the tree when you render the model. The easiest way to do this is to explode the tree component. If you want to have it "always face camera" again, you will need to create a component from it after exploding it. (If this idea catches on, we can create an option to create trees which do not re-render)

4. Then right click on the tree image, select "IRender: Edit Material" and make it transparent.

Then when you render the scene, the trees will be transparent.

- If you want shadows on the trees, you will have to create a shadows mask when creating the tree component.

- This still won't work properly for overlapping trees. If you want overlapping trees, you will need to create an image of the overlapping trees and place in into SketchUp. (You can grab the image of the tree from the SketchUp Material Window.) Combine the images in a Paint program, and then create a new image with multiple, overlapping trees, place it in SketchUp and make it transparent.

Here I have placed two overlapping trees on the right (without using the method described above). They are less transparent the the single tree on the left, because each of the overlapping tree images is processed separately.)