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+==== Perspective ====
+by Bitbreaker/Oxyron/Nuance
+Best is to calculate the perspective during multiply with the rotation matrix. As soon as you get the value for Z, lookup a corresponding factor in a table and multply the results for X and Y with that factor:
+<code>
+        ... matrix multipplication for Z ...
+        tay
+        lda z_fact,y
+        sta z1
+        eor #$ff
+        sta z2
+        ... matrix multiplication for X ...
+        tay
+        ;multiply with z_fact
+        lda (z1),y
+        sec
+        sbc (z2),y
+        sta final_x
+        ... matrix multiplication for Z ...
+        tay
+        ;multiply with z_fact
+        lda (z1),y
+        sec
+        sbc (z2),y
+        sta final_y
+</code>
+The factor-table you could generate like the following:
+<code>
+    ...
+    d = 280.0; z0 = 5.0;
+    for (i = 0; i < 0x100; i++) {
+        z = i;
+        //make things signed
+        if(z > 127) z = z - 256;
+        q = round(d/(z0-z/64.0));
+        //take care that values are sane
+        if(q > 127) q = 127;
+        if(q < -127) q = -127;
+        if(q < 0) q = 256 + q;
+        result[i] = q;
+    }
+    ...
+</code>