From cb15709551921e111d2648f7d6545e4d0e3fdcd6 Mon Sep 17 00:00:00 2001 From: tslil clingman <> Date: Sun, 10 Oct 2021 15:31:36 -0400 Subject: Refactor: extract rendering code from Player struct into Renderer Some bonus off by ones and rounding corrections --- src/render.zig | 456 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 456 insertions(+) create mode 100644 src/render.zig (limited to 'src/render.zig') diff --git a/src/render.zig b/src/render.zig new file mode 100644 index 0000000..12af775 --- /dev/null +++ b/src/render.zig @@ -0,0 +1,456 @@ +// This file is part of ZiRC +// +// Copyright (C) 2021, tslil clingman +// +// This program is free software: you can redistribute it and/or modify +// it under the terms of the GNU General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. +// +// This program is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. +// +// You should have received a copy of the GNU General Public License +// along with this program. If not, see . + +const std = @import("std"); + +const RenderWindow = @import("sfml").graphics.RenderWindow; +const Sprite = @import("sfml").graphics.Sprite; +const Texture = @import("sfml").graphics.Texture; +const Image = @import("sfml").graphics.Image; +const Colour = @import("sfml").graphics.Color; + +const level = @import("level.zig"); +const constants = @import("constants.zig"); +const player = @import("player.zig"); + +fn playerDistComp(pos: [2]f32, lhs: level.Object, rhs: level.Object) bool { + const lx = lhs.pos_x - pos[0]; + const ly = lhs.pos_y - pos[1]; + const rx = rhs.pos_x - pos[0]; + const ry = rhs.pos_y - pos[1]; + + return (lx * lx + ly * ly > rx * rx + ry * ry); +} + +fn fasterColourBlend(onto: Colour, from: Colour) Colour { + const af: u16 = from.a; + const of: u16 = onto.a; + + const ablend: u16 = @divTrunc(of * (255 - af), 255); + const na: u16 = af + ablend; + if (na == 0) return Colour.Black; + + const rf: u16 = from.r; + const ro: u16 = onto.r; + const gf: u16 = from.g; + const go: u16 = onto.g; + const bf: u16 = from.b; + const bo: u16 = onto.b; + + // The most accurate i've found is + const nr = @divTrunc(ro * ablend + rf * af, na); + const ng = @divTrunc(go * ablend + gf * af, na); + const nb = @divTrunc(bo * ablend + bf * af, na); + + // These computations are incorrect, but faster + // const nr = (af * rf + (255 - af) * ro) / 255; + // const ng = (af * gf + (255 - af) * go) / 255; + // const nb = (af * bf + (255 - af) * bo) / 255; + + return Colour{ + .a = @intCast(u8, na), + .r = @intCast(u8, nr), + .g = @intCast(u8, ng), + .b = @intCast(u8, nb), + }; +} + +pub fn Renderer(PlaneWidth: f32, PlaneHeight: f32) type { + const FOV: f32 = std.math.pi / 3.0; + const PlanePixels = PlaneWidth * PlaneHeight; + // given the desired width of the image, how far away must + // the projection plane be from the camera? + const FOV_SCALE = 2 * std.math.tan(FOV / 2); + const PlaneDist = PlaneWidth / FOV_SCALE; + + return struct { + z_buffer: [PlanePixels]f32, + + pub fn new() @This() { + return Renderer(PlaneWidth, PlaneHeight){ + .z_buffer = [_]f32{std.math.inf(f32)} ** PlanePixels, + }; + } + + pub fn renderWorld( + self: *@This(), + plyr: player.Player, + window: RenderWindow, + objects_image: Image, + walls_image: Image, + surfaces_image: Image, + rendered_surfaces_texture: Texture, + rendered_surfaces_sprite: Sprite, + map: level.Map, + ) !void { + // Fist reset the z_buffer + var i: usize = 0; + while (i < self.z_buffer.len) : (i += 1) { + self.z_buffer[i] = std.math.inf(f32); + } + + var pixels = [_]Colour{Colour.Transparent} ** (PlaneWidth * PlaneHeight); + + // Draw all vertical and horizontal surfaces, and populate the z-buffer + self.renderCells(plyr, walls_image, surfaces_image, map, &pixels); + + // use the z_buffer to render sprites + self.renderObjects(plyr, objects_image, map, &pixels); + + try rendered_surfaces_texture.updateFromPixels(&pixels, null); + window.draw(rendered_surfaces_sprite, null); + } + + fn renderObjects( + self: @This(), + plyr: player.Player, + objects_image: Image, + map: level.Map, + pixels: []Colour, + ) void { + const ppos_x = plyr.pos_x; + const ppos_y = plyr.pos_y; + const pheight = plyr.height; + const pcos = std.math.cos(plyr.ang); + const psin = std.math.sin(plyr.ang); + + std.sort.sort(level.Object, map.objects.items, + // Wow, context with an arbitrary type! No macros, just + // Zig all the way down! + [2]f32{ ppos_x, ppos_y }, playerDistComp); + + for (map.objects.items) |obj| { + const ox = obj.pos_x - ppos_x; + const oy = obj.pos_y - ppos_y; + + // We compute the two coordinates of rotating by -self.ang, the + // first of which gives the perpendicular distance to the plane + // of projection, and the second of which gives the + // (unprojected) centre of the object. + const perp_distance = pcos * ox + psin * oy; + const centre = psin * ox - pcos * oy; + + // NOTE: in the below we have applied the magic scaling factor + // of FOV_SCALE. I don't understand how this compensates for the + // linear interpolation incorrectness we do elsewhere, but + // somehow it scales the *correct* values we compute above into + // whatever agrees with the wall and floor rendering voodoo. + + // This quantity is independent of FOV_SCALE because it enters + // both via centre and perp_distance + const proj_centre = PlaneWidth / 2 + PlaneDist * centre / perp_distance; + + // Here's the magic adjustment + const scaled_perp_distance = FOV_SCALE * perp_distance; + const width = PlaneDist * obj.width / scaled_perp_distance; + const left = proj_centre - width / 2; + + // TODO: prune before this? + if (left + width < 0 or left >= PlaneWidth) continue; + + const height = PlaneDist * obj.height / scaled_perp_distance; + const top = PlaneHeight / 2 + PlaneDist * (obj.height - pheight + obj.pos_z) / scaled_perp_distance; + + // TODO: likewise? + if (top < 0 or top - height >= PlaneHeight) continue; + + // Something is on the screen, let's draw it! + const start = std.math.max(0, left); + const end = @floatToInt(usize, std.math.min(left + width, PlaneWidth - 1)); + + const inv_height = 1 / height; + + var tex_frac: f32 = std.math.clamp((start - left) / width, 0, 1); + var col: usize = @floatToInt(usize, start); + const tex_frac_step = 1 / width; + while (col < end) : ({ + col += 1; + tex_frac += tex_frac_step; + }) { + var bottom = std.math.min(top, PlaneHeight); + var pix_y = @floatToInt(usize, std.math.ceil(std.math.max(PlaneHeight - bottom - 1, 0))); + var texel_y = (top - bottom) / height; + while (pix_y < PlaneHeight and bottom >= top - height) : ({ + bottom -= 1; + pix_y += 1; + texel_y += inv_height; + }) { + const index = col * @floatToInt(usize, PlaneHeight) + @floatToInt(usize, bottom); + if (self.z_buffer[index] > scaled_perp_distance) { + const tx = @floatToInt(c_uint, tex_frac * constants.TextureDim); + const toff = obj.texture * @floatToInt(c_uint, constants.TextureDim); + const ty = @floatToInt(c_uint, texel_y * constants.TextureDim); + const texel = objects_image.getPixel(.{ .x = toff + tx, .y = ty }); + const pix_index = @floatToInt(usize, PlaneWidth) * pix_y + col; + // TODO: Decide whether being accurate is as important as being fast + pixels[pix_index] = fasterColourBlend(pixels[pix_index], texel); + } + } + } + } + } + + fn renderCells( + self: *@This(), + plyr: player.Player, + walls_image: Image, + surfaces_image: Image, + map: level.Map, + pixels: []Colour, + ) void { + // This is a TERRIBLE hack: for whatever reason *linearly* + // interpolating on the direction vectors gives + // perspective-correct-seeming walls! + const cos_first = std.math.cos(plyr.ang + 0.5 * FOV); + const cos_last = std.math.cos(plyr.ang - 0.5 * FOV); + const sin_first = std.math.sin(plyr.ang + 0.5 * FOV); + const sin_last = std.math.sin(plyr.ang - 0.5 * FOV); + + const cos_step = (cos_last - cos_first) / PlaneWidth; + const sin_step = (sin_last - sin_first) / PlaneWidth; + + const ppos_x = plyr.pos_x; + const ppos_y = plyr.pos_y; + const pheight = plyr.height; + + var col: u16 = 0; + var cosra = cos_first; + var sinra = sin_first; + while (col < PlaneWidth) : ({ + col += 1; + cosra += cos_step; + sinra += sin_step; + }) { + // Observe that sqrt(1+tan^2) = abs(1/cos) sqrt(cos^2+sin^2) = + // abs(1/cos). Similarly so for cot, hence we obtain the + // following lengths for the hypotenuses assuming that x + // (respectively y) are unit length and the angle is ra. This + // for whatever reasons still works when we linearly interpolate + // on cos and sin! + const dy_for_x_step = std.math.fabs(1 / cosra); + const dx_for_y_step = std.math.fabs(1 / sinra); + + var step_x: i32 = -1; + var step_y: i32 = -1; + + var dist_x: f32 = undefined; + var dist_y: f32 = undefined; + + var ipos_x: i32 = @floatToInt(i32, std.math.floor(ppos_x)); + var ipos_y: i32 = @floatToInt(i32, std.math.floor(ppos_y)); + + // looking right + if (cosra >= 0) { + step_x = 1; + // assuming unit size grid cells + dist_y = (@intToFloat(f32, ipos_x) + 1 - ppos_x) * dy_for_x_step; + } else { + dist_y = (ppos_x - @intToFloat(f32, ipos_x)) * dy_for_x_step; + } + + if (sinra >= 0) { + step_y = 1; + dist_x = (@intToFloat(f32, ipos_y) + 1 - ppos_y) * dx_for_y_step; + } else { + dist_x = (ppos_y - @intToFloat(f32, ipos_y)) * dx_for_y_step; + } + + var top_of_floor: f32 = undefined; + var bottom_of_ceiling: f32 = undefined; + var distance: f32 = 0; + var still_drawing = true; + var highest_drawn: f32 = 0; + var lowest_drawn: f32 = PlaneHeight - 1; + var horizontal_hit: bool = undefined; + while (still_drawing and map.inBounds(ipos_x, ipos_y)) : ({ + // Find the next cell on our path + if (dist_y < dist_x) { + horizontal_hit = false; + distance = dist_y; + dist_y += dy_for_x_step; + ipos_x += step_x; + } else { + horizontal_hit = true; + distance = dist_x; + dist_x += dx_for_y_step; + ipos_y += step_y; + } + }) { + const cell = map.lookup(ipos_x, ipos_y); + + // Are we drawing vertical surfaces? + if (cell.floor_height > 0 or cell.draw_down) { + // project the top of the bottom and the bottom of the top + top_of_floor = PlaneHeight / 2 + PlaneDist * (cell.floor_height - pheight) / distance; + bottom_of_ceiling = PlaneHeight / 2 + PlaneDist * (cell.ceiling_height - pheight) / distance; + + const draw_lower = top_of_floor > highest_drawn; + const draw_upper = cell.draw_down and bottom_of_ceiling < lowest_drawn; + + // Are we able to see any vertical faces? + if (draw_upper or draw_lower) { + // we need the distance to calculate the fractional + // part of the relevant coordinate for texture + // mapping of the walls + const hit_coordinate = if (horizontal_hit) distance * cosra + ppos_x else distance * sinra + ppos_y; + var texfrac = std.math.modf(hit_coordinate).fpart; + + // we also want to be sure that we're consistently orienting + // textures, in this case clockwise + if ((horizontal_hit and sinra < 0) or (!horizontal_hit and cosra > 0)) texfrac = 1 - texfrac; + const texstrip = @floatToInt(c_uint, (constants.TextureDim - 1) * texfrac); + + // height of a unit-height wall at this distance + const nominal_length = PlaneDist / distance; + const inv_nom_len = distance / PlaneDist; + // used for texel indexing + + const td = @floatToInt(c_uint, constants.TextureDim); + if (draw_lower) { + // which texture index? + const t_lower_off = cell.lower_texture * td; + // Note the bizarre rounding we have to do to avoid artifacts + const constrained_top = std.math.min(std.math.floor(top_of_floor), std.math.ceil(lowest_drawn)); + const stop = @floatToInt(i32, highest_drawn); + var zb_y = @floatToInt(i32, constrained_top); + var pix_y = @floatToInt(usize, std.math.ceil(std.math.max(PlaneHeight - constrained_top - 1, 0))); + var texel_y = (top_of_floor - constrained_top) / nominal_length; + + // now we have what we need to draw the face, + // and update the z-buffer + while (zb_y > stop) : ({ + zb_y -= 1; + pix_y += 1; + texel_y += inv_nom_len; + }) { + const ty = @floatToInt(c_uint, std.math.modf(texel_y).fpart * constants.TextureDim); + const texel = walls_image.getPixel(.{ .x = t_lower_off + texstrip, .y = ty }); + + const pix_index = pix_y * @floatToInt(usize, PlaneWidth) + col; + pixels[pix_index] = texel; + + const index = @intCast(usize, col * @floatToInt(i32, PlaneHeight) + zb_y); + self.z_buffer[index] = distance; + } + highest_drawn = top_of_floor; + } + + if (draw_upper) { + const proj_default_end = PlaneHeight / 2 + PlaneDist * (level.Cell.DEFAULT_HEIGHT - pheight) / distance; + const stop = @floatToInt(i32, std.math.min(lowest_drawn, proj_default_end)); + const t_upper_off = cell.upper_texture * td; + const constrained_bottom = std.math.max(bottom_of_ceiling, highest_drawn); + var zb_y = @floatToInt(i32, constrained_bottom); + var pix_y = @floatToInt(usize, std.math.ceil(std.math.max(PlaneHeight - constrained_bottom - 1, 0))); + var texel_y: f32 = 0; + while (zb_y < stop) : ({ + zb_y += 1; + pix_y -= 1; + texel_y += inv_nom_len; + }) { + const ty = @floatToInt(c_uint, (1 - std.math.modf(texel_y).fpart) * (constants.TextureDim - 1)); + const texel = walls_image.getPixel(.{ .x = t_upper_off + texstrip, .y = ty }); + + const pix_index = pix_y * @floatToInt(usize, PlaneWidth) + col; + pixels[pix_index] = texel; + + const index = @intCast(usize, col * @floatToInt(i32, PlaneHeight) + zb_y); + self.z_buffer[index] = distance; + } + lowest_drawn = bottom_of_ceiling; + } + } + } + + // do we potentially draw floor for this cell? + if (highest_drawn < PlaneHeight / 2 or (cell.draw_down and lowest_drawn > PlaneHeight / 2)) { + if (dist_y < dist_x) { + distance = dist_y; + } else { + distance = dist_x; + } + + // Note: next_top can never exceed PlaneHeight / 2 in + // the body of the next block. If the wall is taller + // than us the back edge is lower than the front one so + // this check will fail as we just drew it (or higher + // than it). If the wall is shorter then the back edge + // is at most the horizon. Similarly so for next_bottom + const next_top = PlaneHeight / 2 + PlaneDist * (cell.floor_height - pheight) / distance; + const next_bottom = PlaneHeight / 2 + PlaneDist * (cell.ceiling_height - pheight) / distance; + + // draw floor? + if (next_top > highest_drawn) { + top_of_floor = std.math.ceil(highest_drawn); + const thresh = std.math.min(std.math.min(next_top, lowest_drawn), PlaneHeight / 2 - 1); + while (top_of_floor < thresh) : (top_of_floor += 1) { + const row_dist = (pheight - cell.floor_height) * PlaneDist / (PlaneHeight / 2 - top_of_floor); + const ptop = @floatToInt(usize, top_of_floor); + const itop = @floatToInt(usize, PlaneHeight) - ptop - 1; + + // draw the correct pixel + const sx = std.math.modf(ppos_x + row_dist * cosra); + const sy = std.math.modf(ppos_y + row_dist * sinra); + const toff = cell.floor_texture * @floatToInt(c_uint, constants.TextureDim); + const px = @floatToInt(c_uint, constants.TextureDim * std.math.fabs(sx.fpart)); + const py = @floatToInt(c_uint, constants.TextureDim * std.math.fabs(sy.fpart)); + const val = surfaces_image.getPixel(.{ .x = toff + px, .y = py }); + pixels[itop * @floatToInt(usize, PlaneWidth) + col] = val; + + // record in the z_buffer only if we're above the floor! + if (cell.floor_height > 0) { + const index = col * @floatToInt(usize, PlaneHeight) + ptop; + self.z_buffer[index] = row_dist; + } + } + highest_drawn = next_top; + } + + // draw ceiling? + if (cell.draw_down and next_bottom < lowest_drawn) { + bottom_of_ceiling = std.math.ceil(lowest_drawn); + const thresh = std.math.max(std.math.max(next_bottom, highest_drawn), PlaneHeight / 2 - 1); + while (bottom_of_ceiling > thresh) : (bottom_of_ceiling -= 1) { + const row_dist = (cell.ceiling_height - pheight) * PlaneDist / (bottom_of_ceiling - PlaneHeight / 2); + const ptop = @floatToInt(usize, bottom_of_ceiling); + const itop = @floatToInt(usize, PlaneHeight) - ptop; + + const sx = std.math.modf(ppos_x + row_dist * cosra); + const sy = std.math.modf(ppos_y + row_dist * sinra); + const toff = cell.ceiling_texture * @floatToInt(c_uint, constants.TextureDim); + const px = @floatToInt(c_uint, constants.TextureDim * std.math.fabs(sx.fpart)); + const py = @floatToInt(c_uint, constants.TextureDim * std.math.fabs(sy.fpart)); + const val = surfaces_image.getPixel(.{ .x = toff + px, .y = py }); + pixels[itop * @floatToInt(usize, PlaneWidth) + col] = val; + + if (cell.draw_down) { + const index = col * @floatToInt(usize, PlaneHeight) + ptop; + self.z_buffer[index] = row_dist; + } + } + lowest_drawn = next_bottom; + } + } + } + // Have we filled this column? + if (top_of_floor > lowest_drawn or bottom_of_ceiling < highest_drawn) { + still_drawing = false; + } + } + } + }; +} -- cgit v1.3.1