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https://bugs.freedesktop.org/show_bug.cgi?id=9749
Summary: Drawing smooth lines with 6.5.2 is quite slow comparing
to with 3.3
Product: Mesa
Version: 6.5
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P2
Component: Mesa core
AssignedTo: [email protected]
ReportedBy: [EMAIL PROTECTED]
When glEnable(GL_LINE_SMOOTH) is used, drawing 100000 random antialiased lines
with Mesa-6.5.2 (it takes about 51 second) is quite slow comparing doing the
same with Mesa-3.3 (which takes 7 seconds). Here is my GLUT test program:
------------------------------------------------------------------------
#include <GL/glut.h>
#include "stdlib.h"
static double linewidth = 1.0;
static double r = 0.627451;
static double g = 0.627451;
static double b = 0.627451;
static double a = 1.0;
static double p1[3];
static double p2[3];
static int vport[4] = { 0, 0, 513, 626 };
static float view[6] = { 0.0, 11.0, 0.0, 11.0, -100.0, 10.0 };
void init(void)
{
glEnable (GL_LINE_SMOOTH);
glHint (GL_LINE_SMOOTH_HINT, GL_DONT_CARE);
glLineWidth ( linewidth );
glDisable( GL_LIGHTING );
}
void display(void)
{
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
int i, k;
for( i=0; i<100000; i++ ) {
for( k=0; k<3; k++ ) {
p1[k] = 1+(int)(10.0*rand()/(RAND_MAX+1.0));
p2[k] = 1+(int)(10.0*rand()/(RAND_MAX+1.0));
}
glBegin( GL_LINES );
glColor4d( r, g, b, a );
glVertex3dv( p1 );
glColor4d( r, g, b, a );
glVertex3dv( p2 );
glEnd();
}
p1[0] = 1.0; p1[1] = 0.5; p1[2] = 0.0;
p2[0] = 10.0; p2[1] = 0.5; p2[2] = 0.0;
glBegin( GL_LINES );
glColor4d( r, g, b, a );
glVertex3dv( p1 );
glColor4d( r, g, b, a );
glVertex3dv( p2 );
glEnd();
glFlush();
}
void reshape(int w, int h)
{
glDrawBuffer( GL_BACK );
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
glViewport( vport[0], vport[1], vport[2], vport[3] );
glOrtho( view[0], view[1], view[2], view[3], view[4], view[5] );
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize (vport[2], vport[3]);
glutCreateWindow (argv[0]);
init();
glutReshapeFunc (reshape);
glutDisplayFunc (display);
glutMainLoop();
return 0;
}
------------------------------------------------------------------------
I had looked into this problem a while and found that the time consuming in
Mesa-6.5.2 mainly comes from function compute_coveragef() in file
/Mesa-6.5.2/src/mesa/swrast/s_aaline.c. I made following changes to try to use
the RGBA coverage calculation in Mesa-3.3 in file /Mesa-3.3/src/lnaatemp.h:
- Edit src/mesa/swrast/s_aaline.c, line 483, just before line
"#define NAME(x) aa_ci_##x"
- Add following function:
---------------------------------------------------------------------------------
static void
plot_mae(GLcontext *ctx, struct LineInfo *line, int ix, int iy, GLfloat
coverage)
{
if (coverage == 0.0)
return;
const GLfloat fx = (GLfloat) ix;
const GLfloat fy = (GLfloat) iy;
const GLuint i = line->span.end;
line->span.end++;
line->span.array->coverage[i] = coverage;
line->span.array->x[i] = ix;
line->span.array->y[i] = iy;
line->span.array->rgba[i][RCOMP] = solve_plane_chan(fx, fy, line->rPlane);
line->span.array->rgba[i][GCOMP] = solve_plane_chan(fx, fy, line->gPlane);
line->span.array->rgba[i][BCOMP] = solve_plane_chan(fx, fy, line->bPlane);
line->span.array->rgba[i][ACOMP] = solve_plane_chan(fx, fy, line->aPlane);
if (line->span.end == MAX_WIDTH) {
_swrast_write_rgba_span(ctx, &(line->span));
line->span.end = 0;
}
}
---------------------------------------------------------------------------------
- Edit src/mesa/swrast/s_aalinetemp.h, line 309
- Replace line
"segment(ctx, &line, NAME(plot), 0.0, 1.0);"
with following codes:
---------------------------------------------------------------------------------
#if defined(DO_RGBA)
GLfloat halfWidth = line.halfWidth;
GLint dx = line.dx;
GLint dy = line.dy;
GLint xStep, yStep;
GLfloat fr, fg, fb, fa;
GLfloat dfr, dfg, dfb, dfa;
GLfloat d255 = 1.0F / 255;
fr = (v0->color[0]) * d255;
fg = (v0->color[1]) * d255;
fb = (v0->color[2]) * d255;
fa = (v0->color[3]) * d255;
if (dx < 0) {
xStep = -1;
dx = -dx;
}
else {
xStep = 1;
}
if (dy < 0) {
yStep = -1;
dy = -dy;
}
else {
yStep = 1;
}
if (dx > dy) {
GLint ii;
GLint x = (GLint) line.x0;
GLfloat y = line.y0;
const GLfloat invDx = 1.0F / dx;
GLfloat yStep = (line.y1 - y) * invDx;
dfr = ((v1->color[0]) * d255 - fr) * invDx;
dfg = ((v1->color[1]) * d255 - fg) * invDx;
dfb = ((v1->color[2]) * d255 - fb) * invDx;
dfa = ((v1->color[3]) * d255 - fa) * invDx;
for (ii = 0; ii < dx; ii++) {
GLfloat yTop = y + halfWidth;
GLfloat yBot = y - halfWidth;
GLint yTopi = (GLint) yTop;
GLint yBoti = (GLint) yBot;
GLint iy;
GLfloat alpha = fa;
GLfloat coverage;
ASSERT(yBoti <= yTopi);
{
coverage = (GLfloat) (alpha * (1.0F - (yBot - yBoti)));
plot_mae(ctx, &line, x, yBoti, coverage);
yBoti++;
coverage = (GLfloat) (alpha * (yTop - yTopi));
plot_mae(ctx, &line, x, yTopi, coverage);
yTopi--;
coverage = alpha;
for (iy = yBoti; iy <= yTopi; iy++) {
plot_mae(ctx, &line, x, iy, coverage);
}
}
x += xStep;
y += yStep;
fr += dfr;
fg += dfg;
fb += dfb;
fa += dfa;
}
}
else {
GLint ii;
GLint y = (GLint) line.y0;
GLfloat x = line.x0;
const GLfloat invDy = 1.0F / dy;
GLfloat xStep = (line.x1 - x) * invDy;
dfr = ((v1->color[0]) * d255 - fr) * invDy;
dfg = ((v1->color[1]) * d255 - fg) * invDy;
dfb = ((v1->color[2]) * d255 - fb) * invDy;
dfa = ((v1->color[3]) * d255 - fa) * invDy;
for (ii = 0; ii < dy; ii++) {
GLfloat xRight = x + halfWidth;
GLfloat xLeft = x - halfWidth;
GLint xRighti = (GLint) xRight;
GLint xLefti = (GLint) xLeft;
GLint ix;
GLfloat alpha = fa;
GLfloat coverage;
ASSERT(xLefti < xRight);
{
coverage = (GLfloat) (alpha * (1.0F - (xLeft - xLefti)));
plot_mae(ctx, &line, xLefti, y, coverage);
xLefti++;
coverage = (GLfloat) (alpha * (xRight - xRighti));
plot_mae(ctx, &line, xRighti, y, coverage);
xRighti--;
coverage = alpha;
for (ix = xLefti; ix <= xRighti; ix++) {
plot_mae(ctx, &line, ix, y, coverage);
}
}
x += xStep;
y += yStep;
fr += dfr;
fg += dfg;
fb += dfb;
fa += dfa;
}
}
#else
segment(ctx, &line, NAME(plot), 0.0, 1.0);
#endif
---------------------------------------------------------------------------------
The result is positive. After the changes drawing 100000 smooth lines with 6.5.2
takes about 7 seconds. Sure I shoule consider about Depth, Fog, and so on. But
it's clear that function compute_coveragef() slows down drawing smooth lines.
Maybe smooth line quality in 6.5.2 is much better. Smooth lines quality with 3.3
is acceptable for me.
Maybe there is a need in latest Mesa to balance quality and drawing speed for
smooth lines.
Thanks,
Lixing
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