diff --git a/engines/twine/renderer/renderer.cpp b/engines/twine/renderer/renderer.cpp
index 0c55fd1b0d3..dd9a1b933e5 100644
--- a/engines/twine/renderer/renderer.cpp
+++ b/engines/twine/renderer/renderer.cpp
@@ -49,6 +49,10 @@ void Renderer::init(int32 w, int32 h) {
 	_polyTabSize = _engine->height() * 6;
 	_polyTab = (int16 *)malloc(_polyTabSize * sizeof(int16));
 	_colorProgressionBuffer = (int16 *)malloc(_polyTabSize * sizeof(int16));
+
+	memset(_polyTab, 0, sizeof(_polyTabSize * sizeof(int16)));
+	memset(_colorProgressionBuffer, 0, sizeof(_polyTabSize * sizeof(int16)));
+
 	_tabVerticG = &_polyTab[_engine->height() * 0];
 	_tabVerticD = &_polyTab[_engine->height() * 1];
 	_tabx0 = &_polyTab[_engine->height() * 2];
@@ -600,7 +604,7 @@ int16 Renderer::bottomClip(int16 polyRenderType, ComputedVertex** offTabPoly, in
 	return newNbPoints;
 }
 
-int32 Renderer::computePolyMinMax(int16 polyRenderType, ComputedVertex **offTabPoly, int32 numVertices) {
+int32 Renderer::computePolyMinMax(int16 polyRenderType, ComputedVertex **offTabPoly, int32 numVertices, int &vtop, int &vbottom) {
 	const Common::Rect &clip = _engine->_interface->_clip;
 	if (clip.isEmpty()) {
 		return numVertices;
@@ -693,10 +697,13 @@ int32 Renderer::computePolyMinMax(int16 polyRenderType, ComputedVertex **offTabP
 		}
 	}
 
+	vtop = minsy;
+	vbottom = maxsy;
+
 	return clippedNumVertices;
 }
 
-bool Renderer::computePoly(int16 polyRenderType, const ComputedVertex *vertices, int32 numVertices) {
+bool Renderer::computePoly(int16 polyRenderType, const ComputedVertex *vertices, int32 numVertices, int &vtop, int &vbottom) {
 	const int16 *polyTabBegin = _polyTab;
 	const int16 *polyTabEnd = &_polyTab[_polyTabSize - 1];
 	const int16 *colProgressBufStart = _colorProgressionBuffer;
@@ -710,7 +717,7 @@ bool Renderer::computePoly(int16 polyRenderType, const ComputedVertex *vertices,
 
 	ComputedVertex *offTabPoly[] = {_clippedPolygonVertices1, _clippedPolygonVertices2};
 
-	numVertices = computePolyMinMax(polyRenderType, offTabPoly, numVertices);
+	numVertices = computePolyMinMax(polyRenderType, offTabPoly, numVertices, vtop, vbottom);
 	if (numVertices == 0) {
 		return false;
 	}
@@ -1282,7 +1289,7 @@ void Renderer::svgaPolyTriche(int vtop, int32 vsize, uint16 color) const {
 }
 
 void Renderer::renderPolygons(const CmdRenderPolygon &polygon, ComputedVertex *vertices, int vtop, int vbottom) {
-	if (computePoly(polygon.renderType, vertices, polygon.numVertices)) {
+	if (computePoly(polygon.renderType, vertices, polygon.numVertices, vtop, vbottom)) {
 		const int32 vsize = vbottom - vtop + 1;
 		fillVertices(vtop, vsize, polygon.renderType, polygon.colorIndex);
 	}
@@ -1337,7 +1344,7 @@ void Renderer::fillVertices(int vtop, int32 vsize, uint8 renderType, uint16 colo
 	}
 }
 
-bool Renderer::computeSphere(int32 x, int32 y, int32 radius) {
+bool Renderer::computeSphere(int32 x, int32 y, int32 radius, int &vtop, int &vbottom) {
 	if (radius <= 0) {
 		return false;
 	}
@@ -1427,6 +1434,9 @@ bool Renderer::computeSphere(int32 x, int32 y, int32 radius) {
 			++r;
 		}
 
+		vtop = top;
+		vbottom = bottom;
+
 		return true;
 	}
 
@@ -1633,8 +1643,10 @@ bool Renderer::renderModelElements(int32 numOfPrimitives, const BodyData &bodyDa
 
 			radius -= 3;
 
-			if (computeSphere(sphere->x, sphere->y, radius)) {
-				const int32 vsize = 2 * radius;
+			int vtop = -1;
+			int vbottom = -1;
+			if (computeSphere(sphere->x, sphere->y, radius, vtop, vbottom)) {
+				const int32 vsize = vbottom - vtop;
 				fillVertices(sphere->y - radius, vsize, sphere->polyRenderType, sphere->color);
 			}
 			break;
diff --git a/engines/twine/renderer/renderer.h b/engines/twine/renderer/renderer.h
index 0e0e1a3c5a6..e8304c464f6 100644
--- a/engines/twine/renderer/renderer.h
+++ b/engines/twine/renderer/renderer.h
@@ -152,7 +152,7 @@ private:
 	ModelData _modelData;
 
 	bool renderAnimatedModel(ModelData *modelData, const BodyData &bodyData, RenderCommand *renderCmds, const IVec3 &angleVec, const IVec3 &renderPos, Common::Rect &modelRect);
-	bool computeSphere(int32 x, int32 y, int32 radius);
+	bool computeSphere(int32 x, int32 y, int32 radius, int &vtop, int &vbottom);
 	bool renderModelElements(int32 numOfPrimitives, const BodyData &bodyData, RenderCommand **renderCmds, ModelData *modelData, Common::Rect &modelRect);
 	IVec3 longInverseRot(int32 x, int32 y, int32 z);
 	inline IVec3 getCameraAnglePositions(const IVec3 &vec) {
@@ -208,7 +208,7 @@ private:
 	void svgaPolyDith(int vtop, int32 vsize) const;
 	void svgaPolyMarbre(int vtop, int32 vsize, uint16 color) const;
 	void svgaPolyTriche(int vtop, int32 vsize, uint16 color) const;
-	bool computePoly(int16 polyRenderType, const ComputedVertex *vertices, int32 numVertices);
+	bool computePoly(int16 polyRenderType, const ComputedVertex *vertices, int32 numVertices, int &vtop, int &vbottom);
 
 	const RenderCommand *depthSortRenderCommands(int32 numOfPrimitives);
 	uint8 *preparePolygons(const Common::Array<BodyPolygon>& polygons, int32 &numOfPrimitives, RenderCommand **renderCmds, uint8 *renderBufferPtr, ModelData *modelData);
@@ -225,7 +225,7 @@ private:
 	int16 rightClip(int16 polyRenderType, ComputedVertex** offTabPoly, int32 numVertices);
 	int16 topClip(int16 polyRenderType, ComputedVertex** offTabPoly, int32 numVertices);
 	int16 bottomClip(int16 polyRenderType, ComputedVertex** offTabPoly, int32 numVertices);
-	int32 computePolyMinMax(int16 polyRenderType, ComputedVertex **offTabPoly, int32 numVertices);
+	int32 computePolyMinMax(int16 polyRenderType, ComputedVertex **offTabPoly, int32 numVertices, int &vtop, int &vbottom);
 public:
 	Renderer(TwinEEngine *engine);
 	~Renderer();