3 ms·

I do address all of your concerns in the article. For the angle-to-brightness curve, one of my footnotes says: "I believe his code only lacks a step that impl

I do address all of your concerns in the article. For the angle-to-brightness curve, one of my footnotes says: "I believe his code only lacks a step that implements a minimum threshold on the slope before it gets colored--a step that would remove the problems seen in Figure 1 in flat areas." With regards to misinterpretations: "There's a tradeoff between realism and actual topographic information--real shadows can tell you about the relative height of two objects, but nothing about the slope of the land in the shadow itself." (I also mention how you can adapt the rayshading technique for a local model that doesn't have that problem) And later on in that paragraph, about subjectivity: "Thirdly, cartography has an artistic and practical component, and it’s true what reliefshading.com said in the non-computational shade it threw at global models–sometimes, you need to tweak the direction of the light hitting a particular mountain or valley because it looks better."

tabtab 8y ago
I still have to conclude the Andes example as given is misleading. It strongly implies ray-tracing "fixes" the problems shown. A footnote alone can't fix that (or is the wrong way to fix it). This clause under the picture is particularly problematic: "but it's disconnected from the underlying physics of what makes real shadows occur: rays of light not hitting a surface due to another surface in the way." -- As I mentioned, you often DON'T want that effect for the type of map shown, and that alone is not the main cause of the differences in the illustration. I'd bet money I can tweak the brightness-mapping curve to make the left look very similar to the right. (As somebody else mentioned, the actual curve depends on weather and local textures etc. such that both techniques are ultimately rough approximations.)

tabtab 8y ago

I still have to conclude the Andes example as given is misleading. It strongly implies ray-tracing "fixes" the problems shown. A footnote alone can't fix that (or is the wrong way to fix it). This clause under the picture is particularly problematic: "but it's disconnected from the underlying physics of what makes real shadows occur: rays of light not hitting a surface due to another surface in the way." -- As I mentioned, you often DON'T want that effect for the type of map shown, and that alone is not the main cause of the differences in the illustration. I'd bet money I can tweak the brightness-mapping curve to make the left look very similar to the right. (As somebody else mentioned, the actual curve depends on weather and local textures etc. such that both techniques are ultimately rough approximations.)