Updated Bresenham line drawing to match software renderer output
Sam Lantinga
parent
b9d98331c5
commit
a29d3acc9e
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@ -2807,57 +2807,78 @@ SDL_RenderDrawLineF(SDL_Renderer * renderer, float x1, float y1, float x2, float
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return SDL_RenderDrawLinesF(renderer, points, 2);
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}
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static int plotLineLow(SDL_Renderer *renderer, float x0, float y0, float x1, float y1, SDL_bool draw_first, SDL_bool draw_last)
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static int RenderDrawLineBresenham(SDL_Renderer *renderer, int x1, int y1, int x2, int y2, SDL_bool draw_last)
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{
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int retval = 0;
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float dx = x1 - x0;
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float dy = y1 - y0;
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int yi = 1;
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float x, y, D;
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int count = (int)SDL_ceilf(x1 - x0 + 1);
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int i, deltax, deltay, numpixels;
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int d, dinc1, dinc2;
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int x, xinc1, xinc2;
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int y, yinc1, yinc2;
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int retval;
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SDL_bool isstack;
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SDL_FPoint *points = SDL_small_alloc(SDL_FPoint, count, &isstack);
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SDL_FPoint *tmp = points;
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SDL_FPoint *render_points;
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int render_count;
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SDL_FPoint *points;
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deltax = SDL_abs(x2 - x1);
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deltay = SDL_abs(y2 - y1);
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if (deltax >= deltay) {
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numpixels = deltax + 1;
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d = (2 * deltay) - deltax;
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dinc1 = deltay * 2;
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dinc2 = (deltay - deltax) * 2;
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xinc1 = 1;
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xinc2 = 1;
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yinc1 = 0;
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yinc2 = 1;
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} else {
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numpixels = deltay + 1;
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d = (2 * deltax) - deltay;
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dinc1 = deltax * 2;
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dinc2 = (deltax - deltay) * 2;
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xinc1 = 0;
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xinc2 = 1;
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yinc1 = 1;
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yinc2 = 1;
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}
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if (x1 > x2) {
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xinc1 = -xinc1;
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xinc2 = -xinc2;
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}
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if (y1 > y2) {
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yinc1 = -yinc1;
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yinc2 = -yinc2;
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}
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x = x1;
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y = y1;
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if (!draw_last) {
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--numpixels;
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}
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points = SDL_small_alloc(SDL_FPoint, numpixels, &isstack);
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if (!points) {
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return SDL_OutOfMemory();
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}
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for (i = 0; i < numpixels; ++i) {
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points[i].x = (float)x;
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points[i].y = (float)y;
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if (dy < 0) {
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yi = -1;
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dy = -dy;
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}
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D = (2 * dy) - dx;
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y = y0;
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for (x = x0; x <= x1; ++x) {
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tmp->x = x;
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tmp->y = y;
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tmp++;
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if (D > 0) {
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y += yi;
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D += 2 * (dy - dx);
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if (d < 0) {
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d += dinc1;
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x += xinc1;
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y += yinc1;
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} else {
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D += 2*dy;
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d += dinc2;
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x += xinc2;
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y += yinc2;
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}
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}
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render_count = (int)(tmp - points);
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if (!draw_last) {
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--render_count;
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}
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if (draw_first) {
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render_points = points;
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} else {
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render_points = points+1;
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--render_count;
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}
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if (renderer->scale.x != 1.0f || renderer->scale.y != 1.0f) {
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retval = RenderDrawPointsWithRectsF(renderer, render_points, render_count);
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retval = RenderDrawPointsWithRectsF(renderer, points, numpixels);
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} else {
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retval = QueueCmdDrawPoints(renderer, render_points, render_count);
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retval = QueueCmdDrawPoints(renderer, points, numpixels);
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}
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SDL_small_free(points, isstack);
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@ -2865,81 +2886,6 @@ static int plotLineLow(SDL_Renderer *renderer, float x0, float y0, float x1, flo
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return retval;
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}
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static int plotLineHigh(SDL_Renderer *renderer, float x0, float y0, float x1, float y1, SDL_bool draw_first, SDL_bool draw_last)
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{
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int retval = 0;
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float dx = x1 - x0;
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float dy = y1 - y0;
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int xi = 1;
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float x, y, D;
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int count = (int)SDL_ceilf(y1 - y0 + 1);
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SDL_bool isstack;
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SDL_FPoint *points = SDL_small_alloc(SDL_FPoint, count, &isstack);
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SDL_FPoint *tmp = points;
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SDL_FPoint *render_points;
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int render_count;
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if (!points) {
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return SDL_OutOfMemory();
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}
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if (dx < 0) {
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xi = -1;
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dx = -dx;
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}
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D = (2 * dx) - dy;
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x = x0;
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for (y = y0; y <= y1; ++y) {
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tmp->x = x;
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tmp->y = y;
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tmp++;
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if (D > 0) {
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x += xi;
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D += 2 * (dx - dy);
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} else {
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D += 2*dx;
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}
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}
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render_count = (int)(tmp - points);
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if (!draw_last) {
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--render_count;
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}
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if (draw_first) {
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render_points = points;
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} else {
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render_points = points+1;
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--render_count;
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}
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if (renderer->scale.x != 1.0f || renderer->scale.y != 1.0f) {
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retval = RenderDrawPointsWithRectsF(renderer, render_points, render_count);
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} else {
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retval = QueueCmdDrawPoints(renderer, render_points, render_count);
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}
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SDL_small_free(points, isstack);
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return retval;
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}
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static int plotLineBresenham(SDL_Renderer *renderer, float x0, float y0, float x1, float y1, SDL_bool draw_last)
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{
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if (SDL_fabs(y1 - y0) < SDL_fabs(x1 - x0)) {
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if (x0 > x1) {
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return plotLineLow(renderer, x1, y1, x0, y0, draw_last, SDL_TRUE);
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} else {
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return plotLineLow(renderer, x0, y0, x1, y1, SDL_TRUE, draw_last);
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}
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} else {
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if (y0 > y1) {
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return plotLineHigh(renderer, x1, y1, x0, y0, draw_last, SDL_TRUE);
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} else {
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return plotLineHigh(renderer, x0, y0, x1, y1, SDL_TRUE, draw_last);
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}
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}
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}
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static int
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RenderDrawLinesWithRectsF(SDL_Renderer * renderer,
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const SDL_FPoint * points, const int count)
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@ -2997,7 +2943,8 @@ RenderDrawLinesWithRectsF(SDL_Renderer * renderer,
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frect->x += scale_x;
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}
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} else {
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retval += plotLineBresenham(renderer, points[i].x, points[i].y, points[i+1].x, points[i+1].y, draw_last);
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retval += RenderDrawLineBresenham(renderer, (int)points[i].x, (int)points[i].y,
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(int)points[i+1].x, (int)points[i+1].y, draw_last);
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}
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drew_line = SDL_TRUE;
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}
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