Cleanup: Render Module: move header files to main directory

Move headers files from `render/extern/` to `render/`

Part of T73586

source/blender/render/RE_render_ext.h

@@ -0,0 +1,80 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2006 by Blender Foundation
+ * All rights reserved.
+ */
+/** \file
+ * \ingroup render
+ */
+
+#pragma once
+
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+/* this include is for non-render pipeline exports (still old cruft here) */
+/* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ */
+
+/* called by meshtools */
+struct Depsgraph;
+struct ImagePool;
+struct MTex;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* render_texture.c */
+bool RE_texture_evaluate(const struct MTex *mtex,
+                         const float vec[3],
+                         const int thread,
+                         struct ImagePool *pool,
+                         const bool skip_load_image,
+                         const bool texnode_preview,
+                         /* Return arguments. */
+                         float *r_intensity,
+                         float r_rgba[4]) ATTR_NONNULL(1, 2, 7, 8);
+
+void texture_rgb_blend(
+    float in[3], const float tex[3], const float out[3], float fact, float facg, int blendtype);
+float texture_value_blend(float tex, float out, float fact, float facg, int blendtype);
+
+void RE_texture_rng_init(void);
+void RE_texture_rng_exit(void);
+
+/* imagetexture.c */
+void ibuf_sample(struct ImBuf *ibuf, float fx, float fy, float dx, float dy, float result[4]);
+
+/* pointdensity.c */
+struct PointDensity;
+
+void RE_point_density_cache(struct Depsgraph *depsgraph, struct PointDensity *pd);
+
+void RE_point_density_minmax(struct Depsgraph *depsgraph,
+                             struct PointDensity *pd,
+                             float r_min[3],
+                             float r_max[3]);
+
+void RE_point_density_sample(struct Depsgraph *depsgraph,
+                             struct PointDensity *pd,
+                             const int resolution,
+                             float *values);
+
+void RE_point_density_free(struct PointDensity *pd);
+
+void RE_point_density_fix_linking(void);
+
+#ifdef __cplusplus
+}
+#endif