diff --git a/third_party/gldc/src/draw.c b/third_party/gldc/src/draw.c
index f5c7f49cf..b63e1ecc6 100644
--- a/third_party/gldc/src/draw.c
+++ b/third_party/gldc/src/draw.c
@@ -75,22 +75,13 @@ static void generateQuads(SubmissionTarget* target, const GLsizei first, const G
                 *((Float2*)it->uv) = F2ZERO;
             }
 
-            src += stride;	
+            src += stride;
+            it->flags = GPU_CMD_VERTEX;
             it++;
         }
-        
-        // Quads [0, 1, 2, 3] -> Triangles [{0, 1, 2}  {2, 3, 0}]
-        PREFETCH(dst); // TODO: more prefetching?   
-        memcpy_vertex(dst + 5, dst + 0); dst[5].flags = GPU_CMD_VERTEX_EOL;
-        memcpy_vertex(dst + 4, dst + 3); dst[4].flags = GPU_CMD_VERTEX;
-        memcpy_vertex(dst + 3, dst + 2); dst[3].flags = GPU_CMD_VERTEX;
-        
-        dst[2].flags = GPU_CMD_VERTEX_EOL;
-        dst[1].flags = GPU_CMD_VERTEX;
-        dst[0].flags = GPU_CMD_VERTEX;
-        // TODO copy straight to dst??     
-        
-        dst += 6;
+
+        dst[3].flags = GPU_CMD_VERTEX_EOL;
+        dst += 4;
     }
 }
 
@@ -131,7 +122,7 @@ void APIENTRY glDrawArrays(GLenum mode, GLint first, GLsizei count) {
     TRACE();
     if (!count) return;
     
-    submitVertices(count * 6 / 4); // quads -> triangles
+    submitVertices(count);
     generateQuads(&SUBMISSION_TARGET, first, count);
 }
 
diff --git a/third_party/gldc/src/sh4.c b/third_party/gldc/src/sh4.c
index 29ab58cd9..6cb2fd562 100644
--- a/third_party/gldc/src/sh4.c
+++ b/third_party/gldc/src/sh4.c
@@ -39,13 +39,13 @@ GL_FORCE_INLINE float _glFastInvert(float x) {
     return MATH_fsrra(x * x);
 }
 
-GL_FORCE_INLINE void _glPerspectiveDivideVertex(Vertex* vertex, const float h) {
+GL_FORCE_INLINE void _glPerspectiveDivideVertex(Vertex* vertex) {
     TRACE();
 
     const float f = _glFastInvert(vertex->w);
 
     /* Convert to NDC and apply viewport */
-    vertex->xyz[0] = (vertex->xyz[0] * f * 320) + 320;
+    vertex->xyz[0] = (vertex->xyz[0] * f *  320) + 320;
     vertex->xyz[1] = (vertex->xyz[1] * f * -240) + 240;
 
     /* Orthographic projections need to use invZ otherwise we lose
@@ -120,15 +120,191 @@ static volatile uint32_t* QACR = (uint32_t*) 0xFF000038;
 #define V0_VIS (1 << 0)
 #define V1_VIS (1 << 1)
 #define V2_VIS (1 << 2)
+#define V3_VIS (1 << 3)
 
-void SceneListSubmit(Vertex* v2, int n) {
+static void SubmitTriangle(Vertex* v0, Vertex* v1, Vertex* v2, uint8_t visible_mask) {
+    Vertex __attribute__((aligned(32))) scratch[4];
+
+    switch(visible_mask) {
+    case V0_VIS | V1_VIS | V2_VIS: // All vertices visible
+    {
+        _glPerspectiveDivideVertex(v0);
+        _glPushHeaderOrVertex(v0);
+
+        _glPerspectiveDivideVertex(v1);
+        _glPushHeaderOrVertex(v1);
+
+        _glPerspectiveDivideVertex(v2);
+        _glPushHeaderOrVertex(v2);
+    }
+    break;
+    case V0_VIS: // First vertex was visible
+    {
+        Vertex* a = &scratch[0];
+        Vertex* b = &scratch[1];
+
+        _glClipEdge(v0, v1, a);
+        a->flags = GPU_CMD_VERTEX;
+
+        _glClipEdge(v2, v0, b);
+        b->flags = GPU_CMD_VERTEX_EOL;
+
+        _glPerspectiveDivideVertex(v0);
+        _glPushHeaderOrVertex(v0);
+
+        _glPerspectiveDivideVertex(a);
+        _glPushHeaderOrVertex(a);
+
+        _glPerspectiveDivideVertex(b);
+        _glPushHeaderOrVertex(b);
+    }
+    break;
+    case V1_VIS: // Second vertex was visible
+    {
+        /* Second vertex was visible. In self case we need to create a triangle and produce
+            two new vertices: 1-2, and 2-3. */
+        Vertex* a = &scratch[0];
+        Vertex* b = &scratch[1];
+        Vertex* c = &scratch[2];
+
+        memcpy_vertex(c, v1);
+
+        _glClipEdge(v0, v1, a);
+        a->flags = GPU_CMD_VERTEX;
+
+        _glClipEdge(v1, v2, b);
+        b->flags = GPU_CMD_VERTEX_EOL;
+
+        _glPerspectiveDivideVertex(a);
+        _glPushHeaderOrVertex(a);
+
+        _glPerspectiveDivideVertex(c);
+        _glPushHeaderOrVertex(c);
+
+        _glPerspectiveDivideVertex(b);
+        _glPushHeaderOrVertex(b);
+    }
+    break;
+    case V0_VIS | V1_VIS: // First and second vertex were visible
+    {
+        Vertex* a = &scratch[0];
+        Vertex* b = &scratch[1];
+        Vertex* c = &scratch[2];
+
+        memcpy_vertex(c, v1);
+
+        _glClipEdge(v2, v0, b);
+        b->flags = GPU_CMD_VERTEX;
+
+        _glPerspectiveDivideVertex(v0);
+        _glPushHeaderOrVertex(v0);
+
+        _glClipEdge(v1, v2, a);
+        a->flags = GPU_CMD_VERTEX_EOL;
+
+        _glPerspectiveDivideVertex(c);
+        _glPushHeaderOrVertex(c);
+
+        _glPerspectiveDivideVertex(b);
+        _glPushHeaderOrVertex(b);
+
+        _glPerspectiveDivideVertex(a);
+        _glPushHeaderOrVertex(c);
+        _glPushHeaderOrVertex(a);
+    }
+    break;
+    case V2_VIS: // Third vertex was visible
+    {
+        Vertex* a = &scratch[0];
+        Vertex* b = &scratch[1];
+        Vertex* c = &scratch[2];
+
+        memcpy_vertex(c, v2);
+
+        _glClipEdge(v2, v0, a);
+        a->flags = GPU_CMD_VERTEX;
+
+        _glClipEdge(v1, v2, b);
+        b->flags = GPU_CMD_VERTEX;
+
+        _glPerspectiveDivideVertex(a);
+        _glPushHeaderOrVertex(a);
+
+        _glPerspectiveDivideVertex(b);
+        _glPushHeaderOrVertex(b);
+
+        _glPerspectiveDivideVertex(c);
+        _glPushHeaderOrVertex(c);
+    }
+    break;
+    case V0_VIS | V2_VIS: // First and third vertex were visible
+    {
+        Vertex* a = &scratch[0];
+        Vertex* b = &scratch[1];
+        Vertex* c = &scratch[2];
+
+        memcpy_vertex(c, v2);
+        c->flags = GPU_CMD_VERTEX;
+
+        _glClipEdge(v0, v1, a);
+        a->flags = GPU_CMD_VERTEX;
+
+        _glClipEdge(v1, v2, b);
+        b->flags = GPU_CMD_VERTEX;
+
+        _glPerspectiveDivideVertex(v0);
+        _glPushHeaderOrVertex(v0);
+
+        _glPerspectiveDivideVertex(a);
+        _glPushHeaderOrVertex(a);
+
+        _glPerspectiveDivideVertex(c);
+        _glPushHeaderOrVertex(c);
+        _glPerspectiveDivideVertex(b);
+        _glPushHeaderOrVertex(b);
+
+        c->flags = GPU_CMD_VERTEX_EOL;
+        _glPushHeaderOrVertex(c);
+    }
+    break;
+    case V1_VIS | V2_VIS: // Second and third vertex were visible
+    {
+        Vertex* a = &scratch[0];
+        Vertex* b = &scratch[1];
+        Vertex* c = &scratch[2];
+
+        memcpy_vertex(c, v1);
+
+        _glClipEdge(v0, v1, a);
+        a->flags = GPU_CMD_VERTEX;
+
+        _glClipEdge(v2, v0, b);
+        b->flags = GPU_CMD_VERTEX;
+
+        _glPerspectiveDivideVertex(a);
+        _glPushHeaderOrVertex(a);
+
+        _glPerspectiveDivideVertex(c);
+        _glPushHeaderOrVertex(c);
+
+        _glPerspectiveDivideVertex(b);
+        _glPushHeaderOrVertex(b);
+        _glPushHeaderOrVertex(c);
+
+        _glPerspectiveDivideVertex(v2);
+        _glPushHeaderOrVertex(v2);
+    }
+    break;
+    }	
+}
+
+extern int PASSED, CLIPPED, SKIPPED;
+
+void SceneListSubmit(Vertex* v3, int n) {
     TRACE();
-
     /* You need at least a header, and 3 vertices to render anything */
     if(n < 4) return;
 
-    const float h = vid_mode->height;
-
     PVR_SET(SPAN_SORT_CFG, 0x0);
 
     //Set PVR DMA registers
@@ -150,198 +326,93 @@ void SceneListSubmit(Vertex* v2, int n) {
 
     sq = SQ_BASE_ADDRESS;
 
-    for(int i = 0; i < n; ++i, ++v2) {
-        PREFETCH(v2 + 1);
-        switch(v2->flags) {
+    for(int i = 0; i < n; ++i, ++v3) {
+        PREFETCH(v3 + 1);
+        switch(v3->flags) {
         case GPU_CMD_VERTEX_EOL:
             break;
         case GPU_CMD_VERTEX:
             continue;
         default:
-            _glPushHeaderOrVertex(v2);
+            _glPushHeaderOrVertex(v3);
             continue;
         };
 
-        Vertex* const v0 = v2 - 2;
-        Vertex* const v1 = v2 - 1;
+	// Quads [0, 1, 2, 3] -> Triangles [{0, 1, 2}  {2, 3, 0}]
+        Vertex* const v0 = v3 - 3;
+        Vertex* const v1 = v3 - 2;
+        Vertex* const v2 = v3 - 1;
 
         visible_mask = (
             (v0->xyz[2] > -v0->w) << 0 |
             (v1->xyz[2] > -v1->w) << 1 |
-            (v2->xyz[2] > -v2->w) << 2
+            (v2->xyz[2] > -v2->w) << 2 | 
+            (v3->xyz[2] > -v3->w) << 3
         );
-	Vertex __attribute__((aligned(32))) scratch[4];
+        
+        // Stats gathering found that when testing a 64x64x64 sized world, at most
+        //   ~400-500 triangles needed clipping
+        //   ~13% of the triangles in a frame needed clipping (percentage increased when less triangles overall)
+        // Based on this, the decision was made to optimise for rendering quads there 
+        //  were either entirely visible or entirely culled, at the expensive at making
+        //  partially visible quads a bit slower due to needing to be split into two triangles first
+        // Performance measuring indicated that overall FPS improved from this change
+        //  to switching to try to process 1 quad instead of 2 triangles though
+        
+        if (visible_mask == 15) PASSED += 2;
+        else if (visible_mask == 0) SKIPPED += 2;
+        else CLIPPED += 2;
 
         switch(visible_mask) {
-        case V0_VIS | V1_VIS | V2_VIS: /* All vertices visible */
+        case V0_VIS | V1_VIS | V2_VIS | V3_VIS: // All vertices visible
         {
-            _glPerspectiveDivideVertex(v0, h);
+            _glPerspectiveDivideVertex(v0);
             _glPushHeaderOrVertex(v0);
 
-            _glPerspectiveDivideVertex(v1, h);
+            _glPerspectiveDivideVertex(v1);
             _glPushHeaderOrVertex(v1);
 
-            _glPerspectiveDivideVertex(v2, h);
+            v2->flags = GPU_CMD_VERTEX_EOL;
+            _glPerspectiveDivideVertex(v2);
+            _glPushHeaderOrVertex(v2);
+            
+            
+            v2->flags = GPU_CMD_VERTEX;
             _glPushHeaderOrVertex(v2);
-        }
-        break;
-        case V0_VIS: /* First vertex was visible */
-        {
-            Vertex* a = &scratch[0];
-            Vertex* b = &scratch[1];
 
-            _glClipEdge(v0, v1, a);
-            a->flags = GPU_CMD_VERTEX;
-
-            _glClipEdge(v2, v0, b);
-            b->flags = GPU_CMD_VERTEX_EOL;
-
-            _glPerspectiveDivideVertex(v0, h);
+            v3->flags = GPU_CMD_VERTEX;
+            _glPerspectiveDivideVertex(v3);
+            _glPushHeaderOrVertex(v3);
+            
+            v0->flags = GPU_CMD_VERTEX_EOL;
             _glPushHeaderOrVertex(v0);
-
-            _glPerspectiveDivideVertex(a, h);
-            _glPushHeaderOrVertex(a);
-
-            _glPerspectiveDivideVertex(b, h);
-            _glPushHeaderOrVertex(b);
         }
         break;
-        case V1_VIS: /* Second vertex was visible */
-        {
-            /* Second vertex was visible. In self case we need to create a triangle and produce
-                two new vertices: 1-2, and 2-3. */
-            Vertex* a = &scratch[0];
-            Vertex* b = &scratch[1];
-            Vertex* c = &scratch[2];
-
-            memcpy_vertex(c, v1);
-
-            _glClipEdge(v0, v1, a);
-            a->flags = GPU_CMD_VERTEX;
-
-            _glClipEdge(v1, v2, b);
-            b->flags = GPU_CMD_VERTEX_EOL;
-
-            _glPerspectiveDivideVertex(a, h);
-            _glPushHeaderOrVertex(a);
-
-            _glPerspectiveDivideVertex(c, h);
-            _glPushHeaderOrVertex(c);
-
-            _glPerspectiveDivideVertex(b, h);
-            _glPushHeaderOrVertex(b);
-        }
+        
+        case 0: // No vertices visible
         break;
-        case V0_VIS | V1_VIS: /* First and second vertex were visible */
+        
+        default: // Some vertices visible
         {
-            Vertex* a = &scratch[0];
-            Vertex* b = &scratch[1];
-            Vertex* c = &scratch[2];
-
-            memcpy_vertex(c, v1);
-
-            _glClipEdge(v2, v0, b);
-            b->flags = GPU_CMD_VERTEX;
-
-            _glPerspectiveDivideVertex(v0, h);
-            _glPushHeaderOrVertex(v0);
-
-            _glClipEdge(v1, v2, a);
-            a->flags = GPU_CMD_VERTEX_EOL;
-
-            _glPerspectiveDivideVertex(c, h);
-            _glPushHeaderOrVertex(c);
-
-            _glPerspectiveDivideVertex(b, h);
-            _glPushHeaderOrVertex(b);
-
-            _glPerspectiveDivideVertex(a, h);
-            _glPushHeaderOrVertex(c);
-            _glPushHeaderOrVertex(a);
-        }
-        break;
-        case V2_VIS: /* Third vertex was visible */
-        {
-            Vertex* a = &scratch[0];
-            Vertex* b = &scratch[1];
-            Vertex* c = &scratch[2];
-
-            memcpy_vertex(c, v2);
-
-            _glClipEdge(v2, v0, a);
-            a->flags = GPU_CMD_VERTEX;
-
-            _glClipEdge(v1, v2, b);
-            b->flags = GPU_CMD_VERTEX;
-
-            _glPerspectiveDivideVertex(a, h);
-            _glPushHeaderOrVertex(a);
-
-            _glPerspectiveDivideVertex(b, h);
-            _glPushHeaderOrVertex(b);
-
-            _glPerspectiveDivideVertex(c, h);
-            _glPushHeaderOrVertex(c);
-        }
-        break;
-        case V0_VIS | V2_VIS: /* First and third vertex were visible */
-        {
-            Vertex* a = &scratch[0];
-            Vertex* b = &scratch[1];
-            Vertex* c = &scratch[2];
-
-            memcpy_vertex(c, v2);
-            c->flags = GPU_CMD_VERTEX;
-
-            _glClipEdge(v0, v1, a);
-            a->flags = GPU_CMD_VERTEX;
-
-            _glClipEdge(v1, v2, b);
-            b->flags = GPU_CMD_VERTEX;
-
-            _glPerspectiveDivideVertex(v0, h);
-            _glPushHeaderOrVertex(v0);
-
-            _glPerspectiveDivideVertex(a, h);
-            _glPushHeaderOrVertex(a);
-
-            _glPerspectiveDivideVertex(c, h);
-            _glPushHeaderOrVertex(c);
-            _glPerspectiveDivideVertex(b, h);
-            _glPushHeaderOrVertex(b);
-
-            c->flags = GPU_CMD_VERTEX_EOL;
-            _glPushHeaderOrVertex(c);
-        }
-        break;
-        case V1_VIS | V2_VIS: /* Second and third vertex were visible */
-        {
-            Vertex* a = &scratch[0];
-            Vertex* b = &scratch[1];
-            Vertex* c = &scratch[2];
-            Vertex* d = &scratch[3];
-
-            memcpy_vertex(c, v1);
-            memcpy_vertex(d, v2);
-
-            _glClipEdge(v0, v1, a);
-            a->flags = GPU_CMD_VERTEX;
-
-            _glClipEdge(v2, v0, b);
-            b->flags = GPU_CMD_VERTEX;
-
-            _glPerspectiveDivideVertex(a, h);
-            _glPushHeaderOrVertex(a);
-
-            _glPerspectiveDivideVertex(c, h);
-            _glPushHeaderOrVertex(c);
-
-            _glPerspectiveDivideVertex(b, h);
-            _glPushHeaderOrVertex(b);
-            _glPushHeaderOrVertex(c);
-
-            _glPerspectiveDivideVertex(d, h);
-            _glPushHeaderOrVertex(d);
+            // vertices are modified in SubmitTriangle, so need to copy them
+            Vertex __attribute__((aligned(32))) scratch[4];
+            Vertex* a0 = &scratch[0];
+            Vertex* a2 = &scratch[1];
+            memcpy_vertex(a0, v0);
+            memcpy_vertex(a2, v2);
+            
+            visible_mask &= (V0_VIS | V1_VIS | V2_VIS);       
+            v2->flags = GPU_CMD_VERTEX_EOL;
+            SubmitTriangle(v0, v1, v2, visible_mask);
+            
+            visible_mask = (
+                (a2->xyz[2] > -v2->w) << 0 |
+                (v3->xyz[2] > -v3->w) << 1 |
+                (a0->xyz[2] > -a0->w) << 2
+            );         
+            v3->flags = GPU_CMD_VERTEX;
+            a0->flags = GPU_CMD_VERTEX_EOL;
+            SubmitTriangle(a2, v3, a0, visible_mask);
         }
         break;
         }