diff --git a/rendering/vulkan14/vulkan14indirect.cpp b/rendering/vulkan14/vulkan14indirect.cpp
index e6c38c2b..38028907 100644
--- a/rendering/vulkan14/vulkan14indirect.cpp
+++ b/rendering/vulkan14/vulkan14indirect.cpp
@@ -353,7 +353,7 @@ bool vulkan14_renderer::draw_indirect(vk14::instance_cull &Cull, command_set con
 		auto &draws{scene.draws};
 		auto &window{draw.draws_window};
 		auto const size{static_cast<VkDeviceSize>(Count) * draws.stride};
-		auto slice{(window.open && (size <= draws.window)) ? draw.draws_cache.allocate_before(size, draws.stride, window.base + draws.window) : vk14::ring_slice{}};
+		auto slice{(window.open && (size <= draws.window)) ? draw.draws_cache.allocate_before(size, draws.stride, window.base, window.base + draws.window) : vk14::ring_slice{}};
 		if ((false == bool(slice)) && (size <= draws.window))
 		{
 			slice = draw.draws_cache.allocate(size, draws.stride);
diff --git a/rendering/vulkan14/vulkan14memory.cpp b/rendering/vulkan14/vulkan14memory.cpp
index ccd0b1a7..39f5e69a 100644
--- a/rendering/vulkan14/vulkan14memory.cpp
+++ b/rendering/vulkan14/vulkan14memory.cpp
@@ -764,14 +764,14 @@ VkDeviceSize ring_cache::next(VkDeviceSize const Alignment) const
 	return (m_part.offset + m_used + alignment - 1) / alignment * alignment;
 }
 
-ring_slice ring_cache::allocate_before(VkDeviceSize const Size, VkDeviceSize const Alignment, VkDeviceSize const Limit)
+ring_slice ring_cache::allocate_before(VkDeviceSize const Size, VkDeviceSize const Alignment, VkDeviceSize const Base, VkDeviceSize const Limit)
 {
 	if (false == bool(m_part))
 	{
 		return {};
 	}
 	auto const offset{next(Alignment)};
-	if ((offset + Size > m_part.offset + m_part.size) || (offset + Size > Limit))
+	if ((offset < Base) || (offset + Size > m_part.offset + m_part.size) || (offset + Size > Limit))
 	{
 		return {};
 	}
@@ -786,7 +786,7 @@ ring_slice ring_cache::allocate_before(VkDeviceSize const Size, VkDeviceSize con
 
 ring_slice ring_cache::allocate(VkDeviceSize const Size, VkDeviceSize const Alignment)
 {
-	if (auto const slice{allocate_before(Size, Alignment, std::numeric_limits<VkDeviceSize>::max())})
+	if (auto const slice{allocate_before(Size, Alignment, 0, std::numeric_limits<VkDeviceSize>::max())})
 	{
 		return slice;
 	}
@@ -812,7 +812,7 @@ ring_slice ring_cache::allocate(VkDeviceSize const Size, VkDeviceSize const Alig
 			return {};
 		}
 	}
-	return allocate_before(Size, Alignment, std::numeric_limits<VkDeviceSize>::max());
+	return allocate_before(Size, Alignment, 0, std::numeric_limits<VkDeviceSize>::max());
 }
 
 } // namespace vk14
diff --git a/rendering/vulkan14/vulkan14memory.h b/rendering/vulkan14/vulkan14memory.h
index 2f0172e9..9563aaaa 100644
--- a/rendering/vulkan14/vulkan14memory.h
+++ b/rendering/vulkan14/vulkan14memory.h
@@ -293,9 +293,10 @@ class ring_cache
 	void reset(frame_ring *Ring, VkDeviceSize Part);
 	// Size bytes aligned to Alignment (at most 256); empty when the ring is full
 	ring_slice allocate(VkDeviceSize Size, VkDeviceSize Alignment);
-	// the same, only when the slice fits in the part held and ends before Limit (an offset in the buffer); empty, with nothing taken,
-	// otherwise
-	ring_slice allocate_before(VkDeviceSize Size, VkDeviceSize Alignment, VkDeviceSize Limit);
+	// the same, only when the slice fits in the part held and lies within Base to Limit (offsets in the buffer: a window the shaders
+	// index from Base); empty, with nothing taken, otherwise. the part held may lie below Base: a large slice which got a part of its
+	// own opened the window above it
+	ring_slice allocate_before(VkDeviceSize Size, VkDeviceSize Alignment, VkDeviceSize Base, VkDeviceSize Limit);
 
   private:
 	// where the next slice aligned to Alignment would begin in the part held, as an offset in the buffer
diff --git a/rendering/vulkan14/vulkan14scene.cpp b/rendering/vulkan14/vulkan14scene.cpp
index 65b9135a..86a2116a 100644
--- a/rendering/vulkan14/vulkan14scene.cpp
+++ b/rendering/vulkan14/vulkan14scene.cpp
@@ -1852,7 +1852,7 @@ std::uint32_t vulkan14_renderer::push_draw_block()
 	auto &draws{m_context->scene.draws};
 	auto &draw{*m_draw};
 	auto &window{draw.draws_window};
-	auto slice{window.open ? draw.draws_cache.allocate_before(draws.stride, draws.stride, window.base + draws.window) : vk14::ring_slice{}};
+	auto slice{window.open ? draw.draws_cache.allocate_before(draws.stride, draws.stride, window.base, window.base + draws.window) : vk14::ring_slice{}};
 	if (false == bool(slice))
 	{
 		slice = draw.draws_cache.allocate(draws.stride, draws.stride);
@@ -1884,7 +1884,7 @@ std::uint32_t vulkan14_renderer::walk_instances(glm::mat4 const *Modelviews, std
 	auto const capacity{static_cast<std::size_t>(instances.window / instances.stride) - 1};
 	auto const count{std::min(Count, capacity)};
 	auto const size{static_cast<VkDeviceSize>(count) * instances.stride};
-	auto slice{window.open ? draw.instances_cache.allocate_before(size, instances.stride, window.base + instances.window) : vk14::ring_slice{}};
+	auto slice{window.open ? draw.instances_cache.allocate_before(size, instances.stride, window.base, window.base + instances.window) : vk14::ring_slice{}};
 	if (false == bool(slice))
 	{
 		// a new window, which begins with the identity of the draws which aren't instanced, followed by the instances