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Fallback for if GL_ARB_clip_control not available

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If GL_ARB_clip_control not available then [znear, zfar] -> [1, -1] instead of [1, 0] in normalized device coordinates

Thus, Z is still reversed, but not shifted, clipping should still work properly, and conversion to window coordinates does not cause accuracy regression compared to non-reversed Z rendering.
This commit is contained in:
Levi Burner
2023-10-02 18:20:58 -04:00
parent 9868486af0
commit c6961b77d7
3 changed files with 31 additions and 11 deletions
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src/render/render_gl3.c
+25 -7
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@@ -498,7 +498,7 @@ static void initGL3(const mjvScene* scn, const mjrContext* con) {
// common options
glDisable(GL_BLEND);
glEnable(GL_NORMALIZE);
glClipControl(GL_LOWER_LEFT, GL_ZERO_TO_ONE);
if (mjGLAD_GL_ARB_clip_control) glClipControl(GL_LOWER_LEFT, GL_ZERO_TO_ONE);
glEnable(GL_DEPTH_TEST);
glDepthMask(GL_TRUE);
if (scn->flags[mjRND_CULL_FACE]) {
@@ -601,9 +601,15 @@ static void setView(int view, mjrRect viewport, const mjvScene* scn, const mjrCo
// set projection
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// reverse Z rendering mapping [znear, zfar] -> [1, 0]
glTranslatef(0.0f, 0.0f, 0.5f);
glScalef(1.0f, 1.0f, -0.5f);
if (mjGLAD_GL_ARB_clip_control) {
// reverse Z rendering mapping [znear, zfar] -> [1, 0] (ndc)
glTranslatef(0.0f, 0.0f, 0.5f);
glScalef(1.0f, 1.0f, -0.5f);
}
else {
// reverse Z rendering mapping without shift [znear, zfar] -> [1, -1] (ndc)
glScalef(1.0f, 1.0f, -1.0f);
}
glFrustum(cam.frustum_center - halfwidth,
cam.frustum_center + halfwidth,
cam.frustum_bottom,
@@ -682,6 +688,12 @@ void mjr_render(mjrRect viewport, mjvScene* scn, const mjrContext* con) {
0.0f, 0.0f, 1.0f, 0.0f,
0.5f, 0.5f, 0.0f, 1.0f
};
if (!mjGLAD_GL_ARB_clip_control) {
// account for conversion from ndc to window coordinates
biasMatrix[2*4+2] = 0.5;
biasMatrix[3*4+2] = 0.5;
}
float tempMatrix[16], textureMatrix[16];
mjvGeom *thisgeom, tempgeom;
mjvLight *thislight;
@@ -1029,9 +1041,15 @@ void mjr_render(mjrRect viewport, mjvScene* scn, const mjrContext* con) {
// set projection: from light viewpoint
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// reverse Z rendering mapping [znear, zfar] -> [1, 0]
glTranslatef(0.0f, 0.0f, 0.5f);
glScalef(1.0f , 1.0f, -0.5f);
if (mjGLAD_GL_ARB_clip_control) {
// reverse Z rendering mapping [znear, zfar] -> [1, 0] (ndc)
glTranslatef(0.0f, 0.0f, 0.5f);
glScalef(1.0f, 1.0f, -0.5f);
}
else {
// reverse Z rendering mapping without shift [znear, zfar] -> [1, -1] (ndc)
glScalef(1.0f, 1.0f, -1.0f);
}
if (thislight->directional) {
glOrtho(-con->shadowClip, con->shadowClip,
-con->shadowClip, con->shadowClip,