Changed the Displace modifier to calculate the intensity of a texture from

RGB values if they are returned by the texture function. This fixes an issue
reported by several people where Image textures gave no displacement unless
CalcAlpha was turned on.

source/blender/blenkernel/intern/modifier.c

@@ -2299,6 +2299,21 @@ static void get_texture_coords(DisplaceModifierData *dmd, Object *ob,
 	}
 }
 
+static void get_texture_value(Tex *texture, float *tex_co, TexResult *texres)
+{
+	int result_type;
+
+	result_type = multitex_ext(texture, tex_co, NULL,
+	                           NULL, 1, texres);
+
+	/* if the texture gave an RGB value, we assume it didn't give a valid
+	 * intensity, so calculate one (formula from do_material_tex)
+	 */
+	if(result_type & TEX_RGB)
+		texres->tin = (0.35 * texres->tr + 0.45 * texres->tg
+		               + 0.2 * texres->tb);
+}
+
 /* dm must be a CDDerivedMesh */
 static void displaceModifier_do(
                 DisplaceModifierData *dmd, Object *ob,
@@ -2349,7 +2364,7 @@ static void displaceModifier_do(
 		}
 
 		texres.nor = NULL;
-		multitex_ext(dmd->texture, tex_co[i], NULL, NULL, 1, &texres);
+		get_texture_value(dmd->texture, tex_co[i], &texres);
 
 		delta = texres.tin - dmd->midlevel;