broke out nether, heightfading, depth, and edgelines from base primitive

overviewer_core/src/primitives/height-fading.c

@@ -0,0 +1,68 @@
+/* 
+ * This file is part of the Minecraft Overviewer.
+ *
+ * Minecraft Overviewer 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 3 of the License, or (at
+ * your option) any later version.
+ *
+ * Minecraft Overviewer 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 the Overviewer.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "../overviewer.h"
+
+typedef struct {
+    PyObject *black_color;
+    PyObject *white_color;
+} PrimitiveHeightFading;
+
+static int
+height_fading_start(void *data, RenderState *state, PyObject *support) {
+    PrimitiveHeightFading *self = (PrimitiveHeightFading *)data;
+    
+    self->black_color = PyObject_GetAttrString(support, "black_color");
+    self->white_color = PyObject_GetAttrString(support, "white_color");
+    
+    return 0;
+}
+
+static void
+height_fading_finish(void *data, RenderState *state) {
+    PrimitiveHeightFading *self = (PrimitiveHeightFading *)data;
+
+    Py_DECREF(self->black_color);
+    Py_DECREF(self->white_color);
+}
+
+static void
+height_fading_draw(void *data, RenderState *state, PyObject *src, PyObject *mask, PyObject *mask_light) {
+    PrimitiveHeightFading *self = (PrimitiveHeightFading *)data;
+
+    /* do some height fading */
+    PyObject *height_color = self->white_color;
+
+    /* negative alpha => darkness, positive => light */
+    float alpha = (1.0 / (1 + expf((70 - state->z) / 11.0))) * 0.6 - 0.55;
+    
+    if (alpha < 0.0) {
+        alpha *= -1;
+        height_color = self->black_color;
+    }
+    
+    alpha_over_full(state->img, height_color, mask_light, alpha, state->imgx, state->imgy, 0, 0);
+}
+
+RenderPrimitiveInterface primitive_height_fading = {
+    "height-fading", sizeof(PrimitiveHeightFading),
+    height_fading_start,
+    height_fading_finish,
+    NULL,
+    NULL,
+    height_fading_draw,
+};