+
+/*
+ * This is a faster approximation
+ */
+GLfloat
+_swrast_compute_lambda(GLfloat dsdx, GLfloat dsdy, GLfloat dtdx, GLfloat dtdy,
+ GLfloat dqdx, GLfloat dqdy, GLfloat texW, GLfloat texH,
+ GLfloat s, GLfloat t, GLfloat q, GLfloat invQ)
+{
+ GLfloat dsdx2 = (s + dsdx) / (q + dqdx) - s * invQ;
+ GLfloat dtdx2 = (t + dtdx) / (q + dqdx) - t * invQ;
+ GLfloat dsdy2 = (s + dsdy) / (q + dqdy) - s * invQ;
+ GLfloat dtdy2 = (t + dtdy) / (q + dqdy) - t * invQ;
+ GLfloat maxU, maxV, rho, lambda;
+ dsdx2 = FABSF(dsdx2);
+ dsdy2 = FABSF(dsdy2);
+ dtdx2 = FABSF(dtdx2);
+ dtdy2 = FABSF(dtdy2);
+ maxU = MAX2(dsdx2, dsdy2) * texW;
+ maxV = MAX2(dtdx2, dtdy2) * texH;
+ rho = MAX2(maxU, maxV);
+ lambda = LOG2(rho);
+ return lambda;
+}
+
+
+/**
+ * Fill in the span.texcoords array from the interpolation values.
+ * Note: in the places where we divide by Q (or mult by invQ) we're
+ * really doing two things: perspective correction and texcoord
+ * projection. Remember, for texcoord (s,t,r,q) we need to index
+ * texels with (s/q, t/q, r/q).
+ * If we're using a fragment program, we never do the division
+ * for texcoord projection. That's done by the TXP instruction
+ * or user-written code.
+ */
+static void
+interpolate_texcoords(GLcontext *ctx, struct sw_span *span)
+{
+ ASSERT(span->interpMask & SPAN_TEXTURE);
+ ASSERT(!(span->arrayMask & SPAN_TEXTURE));
+
+ if (ctx->Texture._EnabledCoordUnits > 1) {
+ /* multitexture */
+ GLuint u;
+ span->arrayMask |= SPAN_TEXTURE;
+ for (u = 0; u < ctx->Const.MaxTextureUnits; u++) {
+ if (ctx->Texture._EnabledCoordUnits & (1 << u)) {
+ const struct gl_texture_object *obj =ctx->Texture.Unit[u]._Current;
+ GLfloat texW, texH;
+ GLboolean needLambda;
+ if (obj) {
+ const struct gl_texture_image *img = obj->Image[0][obj->BaseLevel];
+ needLambda = (obj->MinFilter != obj->MagFilter)
+ || ctx->FragmentProgram._Enabled;
+ texW = img->WidthScale;
+ texH = img->HeightScale;
+ }
+ else {
+ /* using a fragment program */
+ texW = 1.0;
+ texH = 1.0;
+ needLambda = GL_FALSE;
+ }
+ if (needLambda) {
+ GLfloat (*texcoord)[4] = span->array->texcoords[u];
+ GLfloat *lambda = span->array->lambda[u];
+ const GLfloat dsdx = span->texStepX[u][0];
+ const GLfloat dsdy = span->texStepY[u][0];
+ const GLfloat dtdx = span->texStepX[u][1];
+ const GLfloat dtdy = span->texStepY[u][1];
+ const GLfloat drdx = span->texStepX[u][2];
+ const GLfloat dqdx = span->texStepX[u][3];
+ const GLfloat dqdy = span->texStepY[u][3];
+ GLfloat s = span->tex[u][0];
+ GLfloat t = span->tex[u][1];
+ GLfloat r = span->tex[u][2];
+ GLfloat q = span->tex[u][3];
+ GLuint i;
+ if (ctx->FragmentProgram._Enabled) {
+ /* do perspective correction but don't divide s, t, r by q */
+ const GLfloat dwdx = span->dwdx;
+ GLfloat w = span->w;
+ for (i = 0; i < span->end; i++) {
+ const GLfloat invW = 1.0F / w;
+ texcoord[i][0] = s * invW;
+ texcoord[i][1] = t * invW;
+ texcoord[i][2] = r * invW;
+ texcoord[i][3] = q * invW;
+ lambda[i] = _swrast_compute_lambda(dsdx, dsdy, dtdx, dtdy,
+ dqdx, dqdy, texW, texH,
+ s, t, q, invW);
+ s += dsdx;
+ t += dtdx;
+ r += drdx;
+ q += dqdx;
+ w += dwdx;
+ }
+
+ }
+ else {
+ for (i = 0; i < span->end; i++) {
+ const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+ texcoord[i][0] = s * invQ;
+ texcoord[i][1] = t * invQ;
+ texcoord[i][2] = r * invQ;
+ texcoord[i][3] = q;
+ lambda[i] = _swrast_compute_lambda(dsdx, dsdy, dtdx, dtdy,
+ dqdx, dqdy, texW, texH,
+ s, t, q, invQ);
+ s += dsdx;
+ t += dtdx;
+ r += drdx;
+ q += dqdx;
+ }
+ }
+ span->arrayMask |= SPAN_LAMBDA;
+ }
+ else {
+ GLfloat (*texcoord)[4] = span->array->texcoords[u];
+ GLfloat *lambda = span->array->lambda[u];
+ const GLfloat dsdx = span->texStepX[u][0];
+ const GLfloat dtdx = span->texStepX[u][1];
+ const GLfloat drdx = span->texStepX[u][2];
+ const GLfloat dqdx = span->texStepX[u][3];
+ GLfloat s = span->tex[u][0];
+ GLfloat t = span->tex[u][1];
+ GLfloat r = span->tex[u][2];
+ GLfloat q = span->tex[u][3];
+ GLuint i;
+ if (ctx->FragmentProgram._Enabled) {
+ /* do perspective correction but don't divide s, t, r by q */
+ const GLfloat dwdx = span->dwdx;
+ GLfloat w = span->w;
+ for (i = 0; i < span->end; i++) {
+ const GLfloat invW = 1.0F / w;
+ texcoord[i][0] = s * invW;
+ texcoord[i][1] = t * invW;
+ texcoord[i][2] = r * invW;
+ texcoord[i][3] = q * invW;
+ lambda[i] = 0.0;
+ s += dsdx;
+ t += dtdx;
+ r += drdx;
+ q += dqdx;
+ w += dwdx;
+ }
+ }
+ else if (dqdx == 0.0F) {
+ /* Ortho projection or polygon's parallel to window X axis */
+ const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+ for (i = 0; i < span->end; i++) {
+ texcoord[i][0] = s * invQ;
+ texcoord[i][1] = t * invQ;
+ texcoord[i][2] = r * invQ;
+ texcoord[i][3] = q;
+ lambda[i] = 0.0;
+ s += dsdx;
+ t += dtdx;
+ r += drdx;
+ }
+ }
+ else {
+ for (i = 0; i < span->end; i++) {
+ const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+ texcoord[i][0] = s * invQ;
+ texcoord[i][1] = t * invQ;
+ texcoord[i][2] = r * invQ;
+ texcoord[i][3] = q;
+ lambda[i] = 0.0;
+ s += dsdx;
+ t += dtdx;
+ r += drdx;
+ q += dqdx;
+ }
+ }
+ } /* lambda */
+ } /* if */
+ } /* for */