Select additive blending if TXF_ADD textures.

src/textures.c

@@ -79,7 +79,7 @@ int txbind( Texture *tx, int *enabled )
     tx->report &= ~(1<<ctx);
   }
 #endif
-  wantblend = (tx->flags & (TXF_ALPHA|TXF_INTENSITY)) ? BLEND_ON : BLEND_OFF;
+  wantblend = (tx->flags & (TXF_ALPHA|TXF_INTENSITY|TXF_ADD)) ? BLEND_ON : BLEND_OFF;
 
   wantenv =
 	  tx->apply == TXF_DECAL ? GL_DECAL
@@ -184,9 +184,14 @@ int txbind( Texture *tx, int *enabled )
   if(wanted != *enabled) {
     if(wanted & BLEND_ON) {
 	glEnable( GL_BLEND );
-	glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
-	glEnable( GL_ALPHA_TEST );
-	glAlphaFunc( GL_GREATER, 0.03 );
+	if(tx->flags & TXF_ADD) {
+	    glBlendFunc( GL_SRC_ALPHA, GL_ONE );
+	    glDisable( GL_ALPHA_TEST );
+	} else {
+	    glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
+	    glEnable( GL_ALPHA_TEST );
+	    glAlphaFunc( GL_GREATER, 0.03 );
+	}
     } else if(wanted & BLEND_OFF) {
 	glDisable( GL_BLEND );
 	glDisable(GL_ALPHA_TEST);