From a795084f84e4bc8fc9695eeb3fd478c04bc913dc Mon Sep 17 00:00:00 2001 From: havoc Date: Tue, 28 Jan 2003 02:13:37 +0000 Subject: [PATCH] added a lot of comments to lightning beam code git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@2708 d7cf8633-e32d-0410-b094-e92efae38249 --- cl_main.c | 46 ++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 40 insertions(+), 6 deletions(-) diff --git a/cl_main.c b/cl_main.c index 0a084b9d..f23ebcc6 100644 --- a/cl_main.c +++ b/cl_main.c @@ -993,9 +993,13 @@ void R_LightningBeams_Init(void) void R_CalcLightningBeamPolygonVertices(float *v, float *tc, const float *start, const float *end, const float *offset, float t1, float t2) { + // near right corner VectorAdd (start, offset, (v + 0));tc[ 0] = 0;tc[ 1] = t1; + // near left corner VectorSubtract(start, offset, (v + 4));tc[ 4] = 1;tc[ 5] = t1; + // far left corner VectorSubtract(end , offset, (v + 8));tc[ 8] = 1;tc[ 9] = t2; + // far right corner VectorAdd (end , offset, (v + 12));tc[12] = 0;tc[13] = t2; } @@ -1029,44 +1033,74 @@ void R_DrawLightningBeamCallback(const void *calldata1, int calldata2) m.tex[0] = R_GetTexture(r_lightningbeamtexture); R_Mesh_State(&m); R_Mesh_Matrix(&r_identitymatrix); + + // calculate beam direction (beamdir) vector and beam length + // get difference vector VectorSubtract(b->end, b->start, beamdir); + // find length of difference vector length = sqrt(DotProduct(beamdir, beamdir)); + // calculate scale to make beamdir a unit vector (normalized) t1 = 1.0f / length; + // scale beamdir so it is now normalized VectorScale(beamdir, t1, beamdir); + + // calculate up vector such that it points toward viewer, and rotates around the beamdir + // get direction from start of beam to viewer VectorSubtract(r_origin, b->start, up); + // remove the portion of the vector that moves along the beam + // (this leaves only a vector pointing directly away from the beam) t1 = -DotProduct(up, beamdir); VectorMA(up, t1, beamdir, up); + // now we have a vector pointing away from the beam, now we need to normalize it VectorNormalizeFast(up); + // generate right vector from forward and up, the result is already normalized + // (CrossProduct returns a vector of multiplied length of the two inputs) CrossProduct(beamdir, up, right); - //VectorVectors(beamdir, right, up); + // calculate T coordinate scrolling (start and end texcoord along the beam) t1 = cl.time * -r_lightningbeam_scroll.value; t1 = t1 - (int) t1; t2 = t1 + beamrepeatscale * length; - // horizontal + // the beam is 3 polygons in this configuration: + // 2 3 + // * * + // 1****** + // * * + // * * + // they are showing different portions of the beam texture, creating an + // illusion of a beam that appears to curl around in 3D space + // (and realize that the whole polygon assembly orients itself to face + // the viewer) + + // polygon 1, verts 0-3 VectorScale(right, r_lightningbeam_thickness.value, offset); R_CalcLightningBeamPolygonVertices(varray_vertex, varray_texcoord[0], b->start, b->end, offset, t1, t2); - // diagonal up-right/down-left + + // polygon 2, verts 4-7 VectorAdd(right, up, offset); VectorScale(offset, r_lightningbeam_thickness.value * 0.70710681f, offset); R_CalcLightningBeamPolygonVertices(varray_vertex + 16, varray_texcoord[0] + 16, b->start, b->end, offset, t1 + 0.33, t2 + 0.33); - // diagonal down-right/up-left + + // polygon 3, verts 8-11 VectorSubtract(right, up, offset); VectorScale(offset, r_lightningbeam_thickness.value * 0.70710681f, offset); R_CalcLightningBeamPolygonVertices(varray_vertex + 32, varray_texcoord[0] + 32, b->start, b->end, offset, t1 + 0.66, t2 + 0.66); if (fogenabled) { + // per vertex colors if fog is used GL_UseColorArray(); R_FogLightningBeamColors(varray_vertex, varray_color, 12, r_lightningbeam_color_red.value, r_lightningbeam_color_green.value, r_lightningbeam_color_blue.value, 1); } else + { + // solid color if fog is not used GL_Color(r_lightningbeam_color_red.value, r_lightningbeam_color_green.value, r_lightningbeam_color_blue.value, 1); + } - //qglDisable(GL_CULL_FACE); + // draw the 3 polygons as one batch of 6 triangles using the 12 vertices R_Mesh_Draw(12, 6, r_lightningbeamelements); - //qglEnable(GL_CULL_FACE); } void R_DrawLightningBeams (void) -- 2.39.2