43 lines
1.6 KiB
Plaintext
43 lines
1.6 KiB
Plaintext
shader_type canvas_item;
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uniform sampler2D tile_atlas : hint_normal;
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uniform sampler2D palette : hint_normal;
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// uniform float tile_width = 8.0;
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uniform float tilemap_width = 512.0; // Require square tilemap for now
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const float index_scale = 255.0 / 16.0;
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// This shader maps from tileID texels to Tiles, and then applies palette.
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// tiles hardcoded to 16x16 tiles for now
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// palette hardcoded to 16x16 colors for now
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vec2 get_tile_atlas_uv(float tile_id, vec2 uv) {
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float tile_idx16 = tile_id * index_scale; // Rescale from [0.0, 1.0] to [0, 255] to [0, 15.9375 (15+15/16)]
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float tile_row = trunc(tile_idx16) / 16.0;
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float tile_col = fract(tile_idx16);
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vec2 tile_uv = vec2(tile_col, tile_row); // Convert 15.9375 to vec2(0.9375==15/16, (15)/16), this should result in integer coordinates in [0,15] scaled to [0,15/16] for UV
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vec2 sub_tile_uv = fract(uv * tilemap_width) / 16.0;
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// TODO: add sea HScroll, waterfall VScroll tile UV modulation
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return tile_uv + sub_tile_uv;
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// return sub_tile_uv + vec2(0.0, 0.5);
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}
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void fragment() {
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// GLES2
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// vec2 uv_tile = trunc(UV * tilemap_width) / tilemap_width;
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vec2 uv_tile = UV;
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float s = texture(TEXTURE, uv_tile).r;
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// TODO: move cycling palette to a sampler2DArray or sampler3D rather than rebinding
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vec2 lut_uv = get_tile_atlas_uv(s, UV);
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float color_id = texture(tile_atlas, lut_uv).r;
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float color_idx16 = color_id * index_scale;
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float pal_row = trunc(color_idx16) / 16.0;
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float pal_col = fract(color_idx16);
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vec2 palette_uv = vec2(pal_col, pal_row);
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COLOR = texture(palette, palette_uv);
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COLOR.a = step(0.000001, color_idx16); // Branchless transparency
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}
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