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Roll Your Own Weeds

Author: BobCox

Tools Needed(Support Programs):

  • TreeDruid
  • Bryce
  • Corel PhotoPaint or other image editor

Step 1 - TreeDruid

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1. Start TreeDruid.

2. Click on the little bush as shown with the yellow rectangle. In lower left hand corner.

3. Click on the little tree outlined in yellow.

4. When you get the window above, set all of your settings as shown here. If there is twist, set it to zero. Be sure to check “include leaves”. IMPORTANT! Write down the “Leaf Length” and the “Leaf Width”. You will use this to size your image/transparent maps.

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5. Click on the “Tropisms” Tab.

6. Now comes the subjective part. Set your Gravity, Wind, and Sun parameters to set the general shape of your bush. These settings will affect how the grass/weeds leaves are oriented. Start with these settings and play. You cannot see the result in this display and must go back and forth between your modeler and TreeDruid to see them. I don't know if the Standalone TreeDruid displays leaf information or not. Careful with the gravity because it will cause some of the grass shoots to go into the ground. More on that later.

7. Believe it or not, you are done with TreeDruid! Click OK and save your object out as a wavefront file. Below is the OBJ as displayed in Ray Dream Studio.

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Step 2 - Bryce - Cleaning up the Mesh

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1. Import the bush (wavefront) file into Bryce. When you get done, it should look something like the image above.

2. We have to delete the branches, trunk, end caps, and stems. To do this, click on the little down arrow as indicated by the yellow rectangle below. If you don't see this at the bottom of your screen, click on the sphere on the far right.

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3. Put your mouse pointer on the “Select Meshes” text in the popup and a second popup will appear. Select each of the meshes indicated by the yellow “D” and hit the delete key.

4. When you are finished, you should have something that looks like the image below.

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5. If you can, start your image editing program now. If you must close out Bryce, save this object by saving your Bryce file.

Step 3 - Painting Your Grass

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Your image editing program is probably different than my own. However, only the very basic tools are used and they are pretty common among the different applications. All we will be using is a basic brush with a texture tip and the masking tools. I am including images from Corel's PhotoPaint 9 to keep me straight. There may be enough similarity to help you use your own image software

1. Remember when I suggested that you write down your leaf width and height. We want to create an image with the same aspect ratio. To do this:

Pick a width for your image. I picked 20 pixels. ( See graphics included in the Weed.zip)


wh = Weed Height = 34.75

ww = Weed Width = 1

ih=Image Height = ?

iw=Image Width = 20

To solve for the height of the graphic with a width of 20 pixels:

wh/ww = ih/iw

or

34.75/1 = ih/20 so by cross multiplying 34.75 * 20 = ih = 695

So create a graphic with a background of pure white.. i.e. 255/255/255 with a width of 20 pixels and a height of 695 pixels.

2. Select a brush and draw in a single weed like I did below. Much of the image is not shown here. You are only seeing the very top. When done, SAVE the image as a bmp, jpeg, or tif file. My file, included in the zip file, is named “weedimageJPG”.

3. a. Create a mask around your stem and head by using the magic wand mask tool and picking in the white area.

b. Invert the mask. You now have a mask around the colored part of your image.

c. Fill or draw a filled rectangle over the mask with black as its color. See the result below.

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4. Save this image as your transparent map. I named my transparent map “weedtransmapJPG”.

We are done here!

Step 4 - Back Into Bryce

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1. Load the Bryce file we saved or bring Bryce to the front of your desktop.

2. Click on the grass mesh to select it.

3. Click on the little “M” in the attributes list.

4. You should look like this.

5. Click in the areas shown in yellow. Set the ambience to 3.3. Also, click where the green rectangle is and check “Blend Transparency”.

6. Click on the little ball above the golden man and you should see this:

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7. Click on the empty box as indicated by 1. Load your “image” file.

8. Click on “Load” as indicated by 2. Load your “transparent” file.

9. If you used white as your background, click on the black/white sphere indicated by 3

Click the check and you are DONE!!!!!! Hahahahahahah!!!! Yipeeeeeee!

Step 5 - Wrap Up

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Performance Tips

Use additional lighting to light your grass/weeds.

Turn off self shadows if you want more detail toward the center of the clump.

Take the wavefront file into a modeler and trim up your grass/weeds by deleting unwanted polygons.

The closer they are to the camera, the slower they render.

Add bump to another channel to give your grass/weeds character.

Please feel free to contact Bob Cox with any questions or feedback.