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[renderer] Make R_BillboarFrame's comments true

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While they weren't entirely false, they were overly verbose and thus
clouded the point.
This commit is contained in:
Bill Currie 2021-12-10 14:54:18 +09:00
parent 3a17e062da
commit 1df3c2eea0
1 changed files with 14 additions and 28 deletions
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42
libs/video/renderer/r_billboard.c
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@ -54,17 +54,12 @@ R_BillboardFrame (entity_t *ent, int orientation, const vec3_t cameravec,
switch (orientation) {
case SPR_FACING_UPRIGHT:
// generate the sprite's axes, with vup straight up in worldspace,
// and bbright perpendicular to cameravec. This will not work if
// the camera origin is directly above the entity origin
// (cameravec is straight up or down), because the cross product
// will be between two nearly parallel vectors and starts to
// approach an undefined state, so we don't draw if the two
// vectors are less than 1 degree apart
// the billboard has its up vector parallel with world up, and
// its right vector perpendicular to cameravec.
// Undefined if the camera is too close to the entity.
VectorNegate (cameravec, tvec);
VectorNormalize (tvec);
dot = tvec[2]; // same as DotProduct (tvec, bbup) because
// bbup is 0, 0, 1
dot = tvec[2]; // DotProduct (tvec, world up)
if ((dot > 0.999848) || (dot < -0.999848)) // cos(1 degree)
return 0;
VectorSet (0, 0, 1, bbup);
@ -75,24 +70,17 @@ R_BillboardFrame (entity_t *ent, int orientation, const vec3_t cameravec,
VectorSet (-bbright[1], bbright[0], 0, bbpn);
break;
case SPR_VP_PARALLEL:
// generate the sprite's axes, completely parallel to the
// viewplane. There are no problem situations, because the
// sprite is always in the same orientation relative to the viewer
// the billboard always has the same orientation as the camera
VectorCopy (vup, bbup);
VectorCopy (vright, bbright);
VectorCopy (vpn, bbpn);
break;
case SPR_VP_PARALLEL_UPRIGHT:
// generate the sprite's axes, with vup straight up in worldspace,
// and bbright parallel to the viewplane.
// This will not work if the view direction is very close to
// straight up or down, because the cross product will be between
// two nearly parallel vectors and starts to approach an undefined
// state, so we don't draw if the two vectors are less than 1
// degree apart
dot = vpn[2]; // same as DotProduct (vpn, bbup) because
// bbup is 0, 0, 1
if ((dot > 0.999848) || (dot < -0.999848)) // cos(1 degree) =
// the billboar has its up vector parallel with world up, and
// its right vector parallel with the view plane.
// Undefined if the camera is looking straight up or down.
dot = vpn[2]; // DotProduct (vpn, world up)
if ((dot > 0.999848) || (dot < -0.999848)) // cos(1 degree)
return 0;
VectorSet (0, 0, 1, bbup);
//CrossProduct(bbup, vpn, bbright)
@ -103,8 +91,8 @@ R_BillboardFrame (entity_t *ent, int orientation, const vec3_t cameravec,
break;
case SPR_ORIENTED:
{
// generate the sprite's axes, according to the sprite's world
// orientation
// The billboard's orientation is fully specified by the
// entity's orientation.
mat4f_t mat;
Transform_GetWorldMatrix (ent->transform, mat);
VectorCopy (mat[0], bbpn);
@ -114,10 +102,8 @@ R_BillboardFrame (entity_t *ent, int orientation, const vec3_t cameravec,
break;
case SPR_VP_PARALLEL_ORIENTED:
{
// generate the sprite's axes, parallel to the viewplane, but
// rotated in that plane around the center according to the
// sprite entity's roll angle. So vpn stays the same, but
// vright and vup rotate
// The billboard is rotated relative to the camera using
// the entity's local rotation.
vec4f_t rot = Transform_GetLocalRotation (ent->transform);
// FIXME needs proper testing (need to find, make, or fake a
// parallel oriented sprite)