diff --git a/overviewer_core/rendermodes.py b/overviewer_core/rendermodes.py
index 2a58255..4b81681 100644
--- a/overviewer_core/rendermodes.py
+++ b/overviewer_core/rendermodes.py
@@ -28,6 +28,11 @@ class RenderPrimitive(object):
             if not key in self.options:
                 raise ValueError("primitive `{0}' has no option `{1}'".format(self.name, key))
             self.option_values[key] = val
+        
+        # set up defaults
+        for name, (description, default) in self.options.iteritems():
+            if not name in self.option_values:
+                self.option_values[name] = default
 
 class Base(RenderPrimitive):
     name = "base"
@@ -44,14 +49,14 @@ class HeightFading(RenderPrimitive):
 class Depth(RenderPrimitive):
     name = "depth"
     options = {
-        "min": "lowest level of blocks to render (default: 0)",
-        "max": "highest level of blocks to render (default: 127)",
+        "min": ("lowest level of blocks to render", 0),
+        "max": ("highest level of blocks to render", 127),
     }
 
 class EdgeLines(RenderPrimitive):
     name = "edge-lines"
     options = {
-        "opacity": "darkness of the edge lines, from 0.0 to 1.0 (default: 0.15)",
+        "opacity": ("darkness of the edge lines, from 0.0 to 1.0", 0.15),
     }
 
 # Render 3 blending masks for lighting
diff --git a/overviewer_core/src/primitives/depth.c b/overviewer_core/src/primitives/depth.c
index 4a2899c..87a14a6 100644
--- a/overviewer_core/src/primitives/depth.c
+++ b/overviewer_core/src/primitives/depth.c
@@ -26,11 +26,8 @@ static int
 depth_start(void *data, RenderState *state, PyObject *support) {
     PrimitiveDepth *self = (PrimitiveDepth *)data;
     
-    self->min = 0;
     if (!render_mode_parse_option(support, "min", "I", &(self->min)))
         return 1;
-
-    self->max = 127;
     if (!render_mode_parse_option(support, "max", "I", &(self->max)))
         return 1;
 
diff --git a/overviewer_core/src/primitives/edge-lines.c b/overviewer_core/src/primitives/edge-lines.c
index 54b7407..f1e4e42 100644
--- a/overviewer_core/src/primitives/edge-lines.c
+++ b/overviewer_core/src/primitives/edge-lines.c
@@ -24,8 +24,6 @@ typedef struct {
 static int
 edge_lines_start(void *data, RenderState *state, PyObject *support) {
     PrimitiveEdgeLines *self = (PrimitiveEdgeLines *)data;
-    
-    self->opacity = 0.15;
     if (!render_mode_parse_option(support, "opacity", "f", &(self->opacity)))
         return 1;
     return 0;
diff --git a/overviewer_core/src/rendermodes.c b/overviewer_core/src/rendermodes.c
index 9a70ba1..6ff99de 100644
--- a/overviewer_core/src/rendermodes.c
+++ b/overviewer_core/src/rendermodes.c
@@ -176,16 +176,16 @@ int render_mode_parse_option(PyObject *support, const char *name, const char *fo
     int ret;
     
     if (support == NULL || name == NULL)
-        return 1;
+        return 0;
     
     dict = PyObject_GetAttrString(support, "option_values");
     if (!dict)
-        return 1;
+        return 0;
     
     item = PyDict_GetItemString(dict, name);
     if (item == NULL) {
         Py_DECREF(dict);
-        return 1;
+        return 0;
     };
     
     /* make sure the item we're parsing is a tuple