If you set it to one, the palette swap will be done at screen level, meaning all appearances of cA will be replaced by cB on the screen at the end of the frame. The l argument is optional and '0' by default. After calling this function, cB will always be drawn instead of cA, until you call the function again to set cA to another color or back to cA, or that you call "pal()" which resets all the colors. In Pico-8, you can do palette swaps using the pal(cA,cB,) function. Note that fades can also be done towards other colors than black and also that this can be used to hide objects on a larger background. Then when drawing the faded surface, you can look up the darker version of a color and then the darker version of this one and so on, to define the current intensity of the fade. Prefer actual normal maps amd shaders if they are an option.Ī good way to do fade-out's and fade-in's with a restricted palette is to define a map of the colors of the palette and that index them to darker versions of themselves inside the palette. However, this method can be very expensive on CPU. Each color of the palette can represent an angle of inclinaison on the surface and then these colors can be colored swapped to the processed lightened colors from the positions of the object and of the light. The texture animation trick can also be used to simulate lighting by simulating a normal map. In the GIF from above, each element of the sprite was forbidden to have the same color as any other neighboring element. The only time costly step to do this is to choose and set the colors you want for each element and then forbid unwanted color combinaisons. Using palette swaps for procedural generation is great because it lets you create a great graphic diversity at very low memory cost, as you do not have to generate a new set of sprite for every new generated instance. It seems each color manipulated in the code is actually an index for a map which itself remaps each color to the color you set it to using the pal() function. In Pico-8, I think the idea is the same except that it works also for drawing lines, circles, etc, not just sprites. In this case, doing a palette swap is as simple as replacing or modifying the associated palette. When actually drawing these surfaces, the system looks up the color for each pixel's color index in the associated palette. Both the colors that need to be replaced and the colors that you want instead should be fed to shader in uniform arrays, or, if you're feeling fancy, in buffers.Ībout the pixel manipulation implementation! This is mostly an educated guess but I believe that in early Nintendo systems (eg: Gameboy Color and NES) as well as in the SDL framework's 8 bit surfaces, surfaces are actually a map of color indexes, associated with a palette. All you need is a fragment shader that replace specific colors with other colors. I think the "shiny" version is slightly more powerful than the regular one but the main difference really is the palette swap.Ī palette swapping shader is actually fairly easy to implement. In Pokemon games, each pokemon species has its own appearance but each species also has a very rare version of itself, called "shiny" and that version uses the original sprites of the regular species only with a palette swap. Pokemon's shiny pokemons are one very elegant example of palette swapping as a content generation tool. The cart and the raw source code will soon be available to download for all my patrons (1$+)! Wanna know even more about palette swapping? Read on! This guide was entirely made in Pico-8! (and then pieced together with Imagemagick)
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