\n<\/p>\n
I am making a ray casting engine with Raylib and I have come across an issue with getting the screen coordinates of the sprite. The code for the sprite handling is as follows.<\/p>\n
void draw_sprites(){\n sprite_t sprite = sprites[0];\n \/\/translate points to players origin\n float dx = sprite.x - player.x;\n float dy = sprite.y - player.y;\n float dz = sprite.z;\n float pa_radians = DEGREE_TO_RADIANS(player.pa);\n float pa_sin = sinf(pa_radians);\n float pa_cos = cosf(pa_radians);\n \/\/ rotated around players angle\n float a=dy*pa_cos+dx*pa_sin;\n float b=dx*pa_cos-dy*pa_sin;\n \/\/ 3d projection onto the screen\n float screen_x = (a \/b)+(project.half_width);\n float screen_y = (dz \/ b)+(project.half_height);\n #ifdef DEBUG\n printf(\"dx = %f, dy = %f a = %f b = %f, screen_y = %f, screen_x %f\\n\",dx,dy,a,b,screen_y,screen_x);\n #endif\n \/\/ for now I am just drawing a rectangle, until I get this sorted out.\n ImageDrawRectangleV(&FrameBuffer, (Vector2){.x = screen_x,.y = screen_y}, (Vector2){.x = 100,.y = 100}, YELLOW);\n}\n<\/code><\/pre>\nMy understanding of the math isn’t the best, but I know my output from this is not accurate, As a sprites aren’t really locked to their map position on the screen.I have logged some data from the output of the math I am doing and it is as follows<\/p>\n
dx = 0.500000, dy = 0.000000 a = 0.000000 b = 0.500000, screen_y = 360.000000, screen_x 640.000000\nplayer x = 1.500000 player y = 1.500000, player.pa = 0.000000\n\/\/one result at 85\nplayer x = 1.500000 player y = 1.500000, player.pa = 85.500000\nsprite x = 2.000000 sprite y = 1.500000 sprite_z = 0.000000\ndx = 0.500000, dy = 0.000000 a = 0.498459 b = 0.039230, screen_y = 360.000000, screen_x 652.706177\n\/\/ another result at 275.00 degrees\ndx = 0.500000, dy = 0.000000 a = -0.497698 b = 0.047923, screen_y = 360.000000, screen_x 629.614624\nplayer x = 1.500000 player y = 1.500000, player.pa = 275.500000\nsprite x = 2.000000 sprite y = 1.500000 sprite_z = 0.000000\n<\/code><\/pre>\nThanks to input from DMGregory, I forgot to mention that the players FOV is fixed to 90 degrees as well, at his request, I decided to also provide the wall and floor casting code.<\/p>\n
\/\/FrameBuffer is just a bitmap that get's updated and sent to the gpu\nImage FrameBuffer;\nTexture FrameText;\n\/\/ this struct is just the data for the screen projection\n\/\/ it gets scaled to the screen's resolution of 1280x720p\n\/\/ if it's not already the same resolution \nstruct{\n int width;\n int height;\n int half_height;\n int half_width;\n}project = {0};\n\/\/ simple DDA raycasting\nvoid raycast(float ray_angle,float raySin, float rayCos,float cosDelta, float sinDelta){\n for(int ray_cnt = 0;ray_cnt < project.width;ray_cnt++){\n int wall = 0;\n float delta_dist_x = fabs(1 \/ rayCos);\n float delta_dist_y = fabs(1\/ raySin);\n float side_dist_x;\n float side_dist_y;\n int step_x;\n int step_y;\n int mapx = (int)player.x;\n int mapy = (int)player.y;\n int side;\n if(rayCos < 0){\n step_x = -1;\n side_dist_x = (player.x - (float)mapx) *delta_dist_x;\n }else{\n step_x = 1;\n side_dist_x = ((float)mapx + 1.0 - player.x) * delta_dist_x;\n }\n if(raySin < 0){\n step_y = -1;\n side_dist_y = (player.y - (float)mapy) *delta_dist_y;\n }else{\n step_y = 1;\n side_dist_y = ((float)mapy + 1.0 - player.y) * delta_dist_y;\n }\n while(!wall){\n if(side_dist_x < side_dist_y){\n side_dist_x += delta_dist_x;\n mapx += step_x;\n side = 0;\n }else{\n side_dist_y += delta_dist_y;\n mapy += step_y;\n side = 1;\n }\n wall = worldMap[mapy][mapx].type;\n }\n cell_t wall_cell = worldMap[mapy][mapx];\n float dist;\n float hitx;\n if(side == 0){\n dist = (side_dist_x - delta_dist_x);\n hitx = player.y + (dist * raySin);\n }\n else{\n dist = (side_dist_y - delta_dist_y);\n hitx = player.x + (dist * rayCos);\n }\n hitx -= floorf(hitx);\n float wall_height = (float)project.half_height \/ dist;\n Vector2 wall_pos = {.x = ray_cnt, .y = project.half_height - wall_height};\n texture_t texture = loaded_textures[wall_cell.texture_id];\n int texture_pos = ((int)(texture.width * hitx) & (texture.width - 1));\n if(!enable_skybox){\n draw_ceiling(ray_cnt, wall_height, rayCos, raySin);\n }\n draw_texture(wall_pos,texture_pos,wall_height,texture);\n\n draw_floor(ray_cnt, wall_height, rayCos, raySin);\n float new_cos = rayCos * cosDelta - raySin * sinDelta;\n raySin = raySin * cosDelta + rayCos * sinDelta;\n rayCos = new_cos;\n ray_angle += rc_data.increment_angle;\n zbuffer[ray_cnt] = dist;\n }\n\/\/ If this doesn't make it apparent I do convert the textures\n\/\/ to column major order\nvoid draw_floor(int x,float wall_height,float rayCos,float raySin){\n float start = project.half_height + wall_height;\n float y = start;\n for(;y < project.height;){\n float dist = project.height \/ (2 * y - project.height);\n float tilex = dist * rayCos;\n float tiley = dist * raySin;\n tilex += player.x;\n tiley += player.y;\n cell_t floor_cell = worldMap[(int)tiley][(int)tilex];\n texture_t floor_text = loa[![ded][1]][1]_textures[floor_cell.texture_id];\n int text_x = (int)(tilex * floor_text.width) & (floor_text.width - 1);\n int text_y = (int)(tiley * floor_text.height) & (floor_text.height - 1);\n ImageDrawPixelV(&FrameBuffer,(Vector2){.x = x,.y = y},floor_text.contents[text_x * floor_text.height + text_y]);\n y++;\n }\n}\n<\/code><\/pre>\nHere is a visual example of the sprite drawing with the sprite and the player at the following values.<\/p>\n
dx = 0.500000, dy = 0.000000 a = 0.000000 b = 0.500000, screen_y = 360.000000, screen_x 640.000000\nplayer x = 1.500000 player y = 1.500000, player.pa = 0.000000\nsprite x = 2.000000 sprite y = 1.500000 sprite_z = 0.000000\n<\/code><\/pre>\n