Creating plant texture maps
I've had to create a large number of plant textures from scratch, and i'd
like to share what i've learned. I am not a professional digital artist,
so you may already have better ideas about how to create plant textures - in
which case, please give me some feedback!
- The texture maps for the plants you need might already available from a
commercial texture vendor such as ImageCELs
or the CGSD RealTexture
- If not, you need to start with good quality photographs.
One you've got the photograph onto your computer, these are steps i do in PhotoShop:
- try to get the whole plant - unobstructed by other objects
- shoot for a background that makes it easy to distinguish the plant
- One way is to try to shoot against a blue sky, but this is often not
possible. The worst case is when there are other plants of similar
color behind your target. I have had some success with arranging a blue
tarp behind the plant, esp. the parts close to the ground that can be most
difficult to tell from the background.
- high resolution - even if the use is eventually for a low-resolution texture
map, the extra resolution will make it that much easier to distinguish the foreground
- crispness - any degree of "fuzziness" due to focus problems, digital camera
compression etc. will make it harder to extract the textures, using a tripod
can help here
- lighting - best time of day is morning or afternoon, shoot with the sun
to your back. If the sky is overcast the bright white background
can throw off the dynamic range of your image, ruining contrast, so try to shoot
on a nice day with direct sunlight.
- consistency - if shooting several different plants, try to keep the light
direction and light quality similar between them. If this isn't possible,
you can sometimes "fix" the lighting later by hand.
- Crop the picture down to just the plant
- Use "Adjust Levels" to adjust the dynamic range. You're going to need
all the brightness and contrast you can get.
- Lasso any large areas that you know aren't part of the plant, and clear
- Now, if you have large areas of blue sky, you may be tempted to use "Select:
Color Range" to select the "blue" and remove them. Beware! This
is a very sloppy approach at best, and can actually make hand editing much more
- Zoom in, and use the Lasso to manually select all surrounding areas that
you know are not part of your plant. I just hold the
shift key and select bit by bit until the plant is surrounded by your selection.
- Hold down shift, and use the Magic Wand tool with a large Tolerance (eg.
50) to select parts of the background that are showing through the plant.
- Once everything but the plant is selected, use "Select: Inverse" and Save
Selection to create an Alpha channel. The new channel will be white for
all areas of the image representing the target plant.
- In the Channels palette, turn on the little "eye" icon next to all the channels.
You can now see more clearly the areas you missed. Go back and add them
to selection, and make the Alpha channel again.
- Now comes the fun part. Deselect all. Highlight the Alpha channel
in the Channel palette. Use the paintbrush and eraser tools to get rid
of every bit of error. The "red" alpha region should extend precisely
up to the edge of the plant but no further.
- To test your results, highlight your RGB channels. Load the selection
from the Alpha channel, copy, create a new file with a colored background, and
- When it looks good, load the selection, invert, and clear to black
- If you've got a symmetric plant you're going to use it for a
X-billboard, resize the canvas until the
axis of symmetry is in the exact center of the image.
- Resize down to an appropriate power of 2 in each dimension.