Original Post
There is a graphics maneuver that seems impossible to complete yet so basic... the very mention of it has put an end to this thread and this post on this forum.
I'll ask again: is there ANY way for Shader Model 2.0 cards to draw Contour Lines - not by crappily applying a 1d texture (that will look horrible... again, look at the first post here) but by using the screen-space derivative functions to do it properly? That functions (ddy, ddx, etc.) do NOT exist on SM 2.0 cards.
How do I proceed? I experimented using a derivative map that I passed along to the shader in a different texture channel, but there were two problems: 1. didn't completely standardize the widths of the lines and they became huge and pixelated when zoomed in (probably a precision problem) and 2. I am going to be animating datasets and interpolating along the time axis; perhaps I implemented it wrong, but it went bonkers when I tried this presumably because the derivate maps can't just be linearly interpolated.. (but shouldn't they be able to?)... there must be a simpler way to draw something as simple as contour lines over a texture! If I color the texture with a palette I can see the boundaries/edges where I want lines, so how do I get LINES?
I'll ask again: is there ANY way for Shader Model 2.0 cards to draw Contour Lines - not by crappily applying a 1d texture (that will look horrible... again, look at the first post here) but by using the screen-space derivative functions to do it properly? That functions (ddy, ddx, etc.) do NOT exist on SM 2.0 cards.
How do I proceed? I experimented using a derivative map that I passed along to the shader in a different texture channel, but there were two problems: 1. didn't completely standardize the widths of the lines and they became huge and pixelated when zoomed in (probably a precision problem) and 2. I am going to be animating datasets and interpolating along the time axis; perhaps I implemented it wrong, but it went bonkers when I tried this presumably because the derivate maps can't just be linearly interpolated.. (but shouldn't they be able to?)... there must be a simpler way to draw something as simple as contour lines over a texture! If I color the texture with a palette I can see the boundaries/edges where I want lines, so how do I get LINES?
