diff options
Diffstat (limited to 'source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl')
| -rw-r--r-- | source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl | 103 |
1 files changed, 44 insertions, 59 deletions
diff --git a/source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl b/source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl index 54a4231590e..b401c3e7b2e 100644 --- a/source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl +++ b/source/blender/draw/engines/overlay/shaders/overlay_grid_frag.glsl @@ -1,6 +1,6 @@ /** * Infinite grid: - * Draw antialiazed grid and axes of different sizes with smooth blending between Level of details. + * Draw antialiased grid and axes of different sizes with smooth blending between levels of detail. * We draw multiple triangles to avoid float precision issues due to perspective interpolation. **/ @@ -8,29 +8,33 @@ #pragma BLENDER_REQUIRE(common_math_lib.glsl) /** - * We want to know how much a pixel is covered by a line. - * We replace the square pixel with acircle of the same area and try to find the intersection area. - * The area we search is the circular segment. https://en.wikipedia.org/wiki/Circular_segment - * The formula for the area uses inverse trig function and is quite complexe. Instead, - * we approximate it by using the smoothstep function and a 1.05 factor to the disc radius. + * We want to know how much of a pixel is covered by a line. + * Here, we imagine the square pixel is a circle with the same area and try to find the + * intersection area. The overlap area is a circular segment. + * https://en.wikipedia.org/wiki/Circular_segment The formula for the area uses inverse trig + * function and is quite complex. Instead, we approximate it by using the smoothstep function and + * a 1.05 factor to the disc radius. + * + * For an alternate approach, see: + * https://developer.nvidia.com/gpugems/gpugems2/part-iii-high-quality-rendering/chapter-22-fast-prefiltered-lines */ #define M_1_SQRTPI 0.5641895835477563 /* 1/sqrt(pi) */ #define DISC_RADIUS (M_1_SQRTPI * 1.05) -#define GRID_LINE_SMOOTH_START (0.5 - DISC_RADIUS) -#define GRID_LINE_SMOOTH_END (0.5 + DISC_RADIUS) +#define GRID_LINE_SMOOTH_START (0.5 + DISC_RADIUS) +#define GRID_LINE_SMOOTH_END (0.5 - DISC_RADIUS) #define GRID_LINE_STEP(dist) smoothstep(GRID_LINE_SMOOTH_START, GRID_LINE_SMOOTH_END, dist) -float get_grid(vec2 co, vec2 fwidthCos, float grid_scale) +float get_grid(vec2 co, vec2 fwidthCos, vec2 grid_scale) { - float half_size = grid_scale / 2.0; + vec2 half_size = grid_scale / 2.0; /* Triangular wave pattern, amplitude is [0, half_size]. */ - vec2 grid_domain = abs(mod(co + half_size, vec2(grid_scale)) - half_size); + vec2 grid_domain = abs(mod(co + half_size, grid_scale) - half_size); /* Modulate by the absolute rate of change of the coordinates * (make line have the same width under perspective). */ grid_domain /= fwidthCos; /* Collapse waves. */ float line_dist = min(grid_domain.x, grid_domain.y); - return 1.0 - GRID_LINE_STEP(line_dist - grid_buf.line_size); + return GRID_LINE_STEP(line_dist - grid_buf.line_size); } vec3 get_axes(vec3 co, vec3 fwidthCos, float line_size) @@ -39,7 +43,7 @@ vec3 get_axes(vec3 co, vec3 fwidthCos, float line_size) /* Modulate by the absolute rate of change of the coordinates * (make line have the same width under perspective). */ axes_domain /= fwidthCos; - return 1.0 - GRID_LINE_STEP(axes_domain - (line_size + grid_buf.line_size)); + return GRID_LINE_STEP(axes_domain - (line_size + grid_buf.line_size)); } #define linearstep(p0, p1, v) (clamp(((v) - (p0)) / abs((p1) - (p0)), 0.0, 1.0)) @@ -91,9 +95,9 @@ void main() } if (flag_test(grid_flag, SHOW_GRID)) { - /* Using `max(dot(dFdxPos, screenVecs[0]), dot(dFdyPos, screenVecs[1]))` + /* Using `max(dot(dFdxPos, ViewMatrixInverse[0]), dot(dFdyPos, ViewMatrixInverse[1]))` * would be more accurate, but not really necessary. */ - float grid_res = dot(dFdxPos, screenVecs[0].xyz); + float grid_res = dot(dFdxPos, ViewMatrixInverse[0].xyz); /* The grid begins to appear when it comprises 4 pixels. */ grid_res *= 4; @@ -106,49 +110,30 @@ void main() grid_res = grid_buf.zoom_factor; } - /* From biggest to smallest. */ - vec4 scale; -#define grid_step(a) grid_buf.steps[a].x -#if 0 /* Inefficient. */ - int step_id = 0; - scale[0] = 0.0; - scale[1] = grid_step(0); - while (scale[1] < grid_res && step_id != STEPS_LEN - 1) { - scale[0] = scale[1]; - scale[1] = grid_step(++step_id); - } - scale[2] = grid_step(min(step_id + 1, STEPS_LEN - 1)); - scale[3] = grid_step(min(step_id + 2, STEPS_LEN - 1)); -#else - /* For more efficiency, unroll the loop above. */ - if (grid_step(0) > grid_res) { - scale = vec4(0.0, grid_step(0), grid_step(1), grid_step(2)); - } - else if (grid_step(1) > grid_res) { - scale = vec4(grid_step(0), grid_step(1), grid_step(2), grid_step(3)); - } - else if (grid_step(2) > grid_res) { - scale = vec4(grid_step(1), grid_step(2), grid_step(3), grid_step(4)); - } - else if (grid_step(3) > grid_res) { - scale = vec4(grid_step(2), grid_step(3), grid_step(4), grid_step(5)); - } - else if (grid_step(4) > grid_res) { - scale = vec4(grid_step(3), grid_step(4), grid_step(5), grid_step(6)); - } - else if (grid_step(5) > grid_res) { - scale = vec4(grid_step(4), grid_step(5), grid_step(6), grid_step(7)); - } - else if (grid_step(6) > grid_res) { - scale = vec4(grid_step(5), grid_step(6), grid_step(7), grid_step(7)); - } - else { - scale = vec4(grid_step(6), grid_step(7), grid_step(7), grid_step(7)); +/** Keep in sync with `SI_GRID_STEPS_LEN` in `DNA_space_types.h`. */ +#define STEPS_LEN 8 + int step_id_x = STEPS_LEN - 1; + int step_id_y = STEPS_LEN - 1; + + /* Loop backwards a compile-time-constant number of steps. */ + for (int i = STEPS_LEN - 2; i >= 0; --i) { + step_id_x = (grid_res < grid_buf.steps[i].x) ? i : step_id_x; /* Branchless. */ + step_id_y = (grid_res < grid_buf.steps[i].y) ? i : step_id_y; } -#endif -#undef grid_step - float blend = 1.0 - linearstep(scale[0], scale[1], grid_res); + /* From biggest to smallest. */ + float scale0x = step_id_x > 0 ? grid_buf.steps[step_id_x - 1].x : 0.0; + float scaleAx = grid_buf.steps[step_id_x].x; + float scaleBx = grid_buf.steps[min(step_id_x + 1, STEPS_LEN - 1)].x; + float scaleCx = grid_buf.steps[min(step_id_x + 2, STEPS_LEN - 1)].x; + + float scale0y = step_id_y > 0 ? grid_buf.steps[step_id_y - 1].y : 0.0; + float scaleAy = grid_buf.steps[step_id_y].y; + float scaleBy = grid_buf.steps[min(step_id_y + 1, STEPS_LEN - 1)].y; + float scaleCy = grid_buf.steps[min(step_id_y + 2, STEPS_LEN - 1)].y; + + /* Subtract from 1.0 to fix blending when `scale0x == scaleAx`. */ + float blend = 1.0 - linearstep(scale0x + scale0y, scaleAx + scaleAy, grid_res + grid_res); blend = blend * blend * blend; vec2 grid_pos, grid_fwidth; @@ -165,9 +150,9 @@ void main() grid_fwidth = fwidthPos.xy; } - float gridA = get_grid(grid_pos, grid_fwidth, scale[1]); - float gridB = get_grid(grid_pos, grid_fwidth, scale[2]); - float gridC = get_grid(grid_pos, grid_fwidth, scale[3]); + float gridA = get_grid(grid_pos, grid_fwidth, vec2(scaleAx, scaleAy)); + float gridB = get_grid(grid_pos, grid_fwidth, vec2(scaleBx, scaleBy)); + float gridC = get_grid(grid_pos, grid_fwidth, vec2(scaleCx, scaleCy)); out_color = colorGrid; out_color.a *= gridA * blend; |