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    Guild Artisan su_liam's Avatar
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    Aug 2007
    Port Alberta, Regina(IRL: Eugene, OR)

    Post An experiment with Wilbur and Bryce

    This is a little experiment I did with building up a terrain. Basically, I started in Wilbur with the default image size(192x192, I think). I used the tesselation tool with a bit of fractal noise to create the initial slope and sketch in the ridgeline. My attempt to create a piedmont and escarpment structure was not altogether successful, but I know what my error was.

    I then used fill-basin to correct the drainage, added a bit of noise to roughen up the flat areas that resulted, then refilled. Next, I looked at the river finding texture to make sure that my streams are decently meandery rather than diving straight down. I repeated the noise-fill-river routine till my river structure looked good to me, then I did an incise flow with a high exponent(2/3 to start with) and a fairly high blur. Here I pretty much followed Waldronate's noise-fill-erode tutorial, decreasing the blur and exponent with each step. Before each incise flow step, I made sure to look at the river flows. At this low res river flow is decently quick and it's miserable to fix a big ugly straight segment after burning it in with incise flow. If I see any ugly spots in the river network, I add noise, fill-basins and look again. Rinse and repeat as necessary. I think somewhere in here I played with precipiton erosion, but hey... My memory is not perfect.

    At this point I used Simple Resample to increase the size of my image to about 1200x1200. Now things slow down a bit, but if I have a good foundation I shouldn't need more than a few iterations to add a bit of detail. Basically, I just repeated what I did on the smaller image, but less so.

    Another resample to 2048. Adding detail here was a bit slow, but it's still a good idea to keep looking at river flow so that things keep looking good.

    I created a straight blend of altitude and slope textures using an atlas-type gradient I found in the Fractal terrains folder. I built a terrain in Bryce using the 16-bit png I exported from Wilbur and textured it with the surface texture just mentioned. The result was the cheerfully-colored image on the right. There was a slight conflict between the lighting direction in the texture and in Bryce. This isn't a bad way to bring out some detail if not too extreme and used in moderation.

    I decided the detail was a bit weak so I resampled to 4k(4096x4096). Adding detail and erosion at this point was glacial, but still worthwhile(I wanna MacPro!!!), so I only did one iteration.

    I used photoshop to create a new texture for Bryce as well as alpha channels to add specularity and reflection to the rivers, some bump height to forest areas, and a higher diffusion value to the icy mountain tops as they tended to go seriously gray. I spent as much time on the texturing as I did on the built-up terrain for a less satisfactory effect. I did like the forest texture, though.

    The texture and HF resolution was 4k for the image on the left.

    I think I'll be using this technique in the future. Starting with a low res image allowed me to get an attractively-eroded terrain quickly, with only a little bit of erosion added at higher resolutions where the tools get boggy. This was a good compromise between quality and time.

    p.s. The best way I've found to iteratively add noise is to add about 5% percentage noise and an absolute magnitude noise of 3-5. The iteration after my first basin fill was more extreme(15%, 12-25). Also, in the left image there is no river coloring, the rivers in the image are altogether the result of reflection effects in the renderer. I'm not altogether convinced that's a good thing. I might multiply in some ps Add Noise on top of the river map I used as an alpha channel for reflection. Hmmm
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