renderer: Improve depth buffer accuracy

Co-authored-by: SaturnSky <ikadro@gmail.com>

vita3k/renderer/src/vulkan/pipeline_cache.cpp

@@ -840,7 +840,6 @@ vk::Pipeline PipelineCache::compile_pipeline(SceGxmPrimitiveType type, vk::Rende
     const bool use_shader_interlock = state.features.support_shader_interlock && gxm_fragment_shader->is_frag_color_used();
 
     const vk::PipelineRasterizationStateCreateInfo rasterizer{
-        .depthClampEnable = state.physical_device_features.depthClamp,
         .polygonMode = translate_polygon_mode(record.front_polygon_mode),
         .cullMode = translate_cull_mode(record.cull_mode),
         // front face is always counter clockwise

vita3k/renderer/src/vulkan/renderer.cpp

@@ -616,7 +616,6 @@ bool VKState::create(std::unique_ptr<renderer::State> &state, const Config &conf
 
         // use these features (because they are used by the vita GPU) if they are available
         vk::PhysicalDeviceFeatures enabled_features{
-            .depthClamp = physical_device_features.depthClamp,
             .fillModeNonSolid = physical_device_features.fillModeNonSolid,
             .wideLines = physical_device_features.wideLines,
             .samplerAnisotropy = physical_device_features.samplerAnisotropy,

vita3k/shader/src/spirv_recompiler.cpp

@@ -1743,6 +1743,9 @@ static spv::Function *make_vert_finalize_function(spv::Builder &b, const SpirvSh
                     z = b.createBinOp(spv::OpFMul, f32, z, z_scale);
                     z = b.createBinOp(spv::OpFAdd, f32, z, z_offset);
 
+                    // z values below 0 get clamped
+                    z = b.createBuiltinCall(f32, utils.std_builtins, GLSLstd450FMax, { z, zero });
+
                     if (!translation_state.is_vulkan) {
                         // convert [0,1] depth range (gxp, vulkan) to [-1,1] depth range (opengl)
                         z = b.createBinOp(spv::OpFMul, f32, z, b.makeFloatConstant(2.0f));