diff --git a/samples/software3d/build.gradle.kts b/samples/software3d/build.gradle.kts
index 8b4f1ccbb..a5d0e257d 100644
--- a/samples/software3d/build.gradle.kts
+++ b/samples/software3d/build.gradle.kts
@@ -39,6 +39,7 @@ teavm.wasm {
     mainClass = "org.teavm.samples.software3d.teavm.WasmWorkerKt"
     optimization = OptimizationLevel.AGGRESSIVE
     minHeapSize = 4
+    maxHeapSize = 32
 }
 
 kotlin {
diff --git a/samples/software3d/src/commonMain/kotlin/org/teavm/samples/software3d/rasterization/Raster.kt b/samples/software3d/src/commonMain/kotlin/org/teavm/samples/software3d/rasterization/Raster.kt
index bf12d3b81..fd91d9508 100644
--- a/samples/software3d/src/commonMain/kotlin/org/teavm/samples/software3d/rasterization/Raster.kt
+++ b/samples/software3d/src/commonMain/kotlin/org/teavm/samples/software3d/rasterization/Raster.kt
@@ -34,4 +34,8 @@ class Raster(@JvmField val width: Int, @JvmField val height: Int) {
         color = IntArray(width * height)
         return result
     }
+
+    companion object {
+        fun calculateHeight(height: Int, step: Int, offset: Int): Int = ((height + step - 2 - offset) / step) + 1
+    }
 }
\ No newline at end of file
diff --git a/samples/software3d/src/commonMain/kotlin/org/teavm/samples/software3d/rasterization/Rasterizer.kt b/samples/software3d/src/commonMain/kotlin/org/teavm/samples/software3d/rasterization/Rasterizer.kt
index c15895f28..a9cb0ec4a 100644
--- a/samples/software3d/src/commonMain/kotlin/org/teavm/samples/software3d/rasterization/Rasterizer.kt
+++ b/samples/software3d/src/commonMain/kotlin/org/teavm/samples/software3d/rasterization/Rasterizer.kt
@@ -104,7 +104,7 @@ class Rasterizer(val raster: Raster, val offset: Int, val step: Int) {
             val ex = s2.pos.x + d2x * k2
             val startIntX = ceil(sx).toInt().coerceAtLeast(0)
             val endIntX = ceil(ex).toInt().coerceAtMost(raster.width)
-            if (startIntX + 1 == endIntX || startIntX >= raster.width || endIntX <= 0) {
+            if (startIntX >= endIntX || startIntX >= raster.width || endIntX <= 0) {
                 y += step
                 continue
             }
diff --git a/samples/software3d/src/jsMain/kotlin/org/teavm/samples/software3d/kjs/worker.kt b/samples/software3d/src/jsMain/kotlin/org/teavm/samples/software3d/kjs/worker.kt
index 6acbd33d0..92db10a01 100644
--- a/samples/software3d/src/jsMain/kotlin/org/teavm/samples/software3d/kjs/worker.kt
+++ b/samples/software3d/src/jsMain/kotlin/org/teavm/samples/software3d/kjs/worker.kt
@@ -42,7 +42,7 @@ private fun init(data: dynamic) {
     val step = data.step as Int
     val offset = data.offset as Int
     val (scene, updaterF) = geometry()
-    raster = Raster(width, height / step)
+    raster = Raster(width, Raster.calculateHeight(height, step, offset))
     updater = updaterF
     renderer = Renderer(scene, raster, offset, step).apply {
         projection = Matrix.projection(-1f, 1f, -1f, 1f, 2f, 10f)
diff --git a/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/swing/swingMain.kt b/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/swing/swingMain.kt
index 0a78822d2..57edfee00 100644
--- a/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/swing/swingMain.kt
+++ b/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/swing/swingMain.kt
@@ -47,10 +47,10 @@ fun main() {
     }
 
     val (scene, updater) = geometry()
-    val taskCount = Runtime.getRuntime().availableProcessors()
+    val taskCount = 1// Runtime.getRuntime().availableProcessors()
     println("Running on $taskCount CPUs")
-    val rasters = (0 until taskCount).map { Raster(SCENE_WIDTH, SCENE_HEIGHT / taskCount) }
-    val renderers = rasters.mapIndexed() { index, raster ->
+    val rasters = (0 until taskCount).map { Raster(SCENE_WIDTH, (SCENE_HEIGHT + taskCount - 1) / taskCount) }
+    val renderers = rasters.mapIndexed { index, raster ->
         Renderer(scene, raster, index, taskCount).apply {
             projection = Matrix.projection(-1f, 1f, -1f, 1f, 2f, 10f)
             viewport = Matrix.translation(SCENE_WIDTH / 2f, SCENE_HEIGHT / 2f, 0f) *
diff --git a/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/teavm/WasmWorker.kt b/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/teavm/WasmWorker.kt
index 4e218eb9f..eaf484807 100644
--- a/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/teavm/WasmWorker.kt
+++ b/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/teavm/WasmWorker.kt
@@ -31,7 +31,7 @@ fun main() {
 @Export(name = "initWorker")
 fun init(width: Int, height: Int, step: Int, offset: Int) {
     val (scene, updaterF) = geometry()
-    raster = Raster(width, height / step)
+    raster = Raster(width, Raster.calculateHeight(height, step, offset))
     updater = updaterF
     renderer = Renderer(scene, raster, offset, step).apply {
         projection = Matrix.projection(-1f, 1f, -1f, 1f, 2f, 10f)
diff --git a/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/teavm/Worker.kt b/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/teavm/Worker.kt
index 47baf9a30..3bf045e98 100644
--- a/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/teavm/Worker.kt
+++ b/samples/software3d/src/jvmMain/kotlin/org/teavm/samples/software3d/teavm/Worker.kt
@@ -49,7 +49,7 @@ class RenderWorker {
         height = (params["height"] as JSNumber).intValue()
         val step = (params["step"] as JSNumber).intValue()
         val offset = (params["offset"] as JSNumber).intValue()
-        raster = Raster(width, height / step)
+        raster = Raster(width, Raster.calculateHeight(height, step, offset))
         updater = updaterF
         renderer = Renderer(scene, raster, offset, step).apply {
             projection = Matrix.projection(-1f, 1f, -1f, 1f, 2f, 10f)