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LibGL: Fix clipping and interpolate vertex attributes

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The previous clipping implementation was problematic especially when
clipping against the near plane. Triangles are now correctly clipped
using homogenous coordinates against all frustum planes.

Texture coordinates and vertex colors are now correctly interpolated.
The earier implementation was just a placeholder.
This commit is contained in:
Stephan Unverwerth 2021-08-16 19:22:08 +02:00 • committed by Andreas Kling
parent 39ff1459f8
commit 220ac5eb02
6 changed files with 111 additions and 205 deletions
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27
Userland/Libraries/LibGL/SoftwareRasterizer.cpp
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@ -107,9 +107,9 @@ static void rasterize_triangle(const RasterizerOptions& options, Gfx::Bitmap& re
VERIFY((render_target.height() % RASTERIZER_BLOCK_SIZE) == 0);
// Calculate area of the triangle for later tests
IntVector2 v0 { (int)triangle.vertices[0].x, (int)triangle.vertices[0].y };
IntVector2 v1 { (int)triangle.vertices[1].x, (int)triangle.vertices[1].y };
IntVector2 v2 { (int)triangle.vertices[2].x, (int)triangle.vertices[2].y };
IntVector2 v0 { (int)triangle.vertices[0].position.x(), (int)triangle.vertices[0].position.y() };
IntVector2 v1 { (int)triangle.vertices[1].position.x(), (int)triangle.vertices[1].position.y() };
IntVector2 v2 { (int)triangle.vertices[2].position.x(), (int)triangle.vertices[2].position.y() };
int area = edge_function(v0, v1, v2);
if (area == 0)
@ -259,7 +259,8 @@ static void rasterize_triangle(const RasterizerOptions& options, Gfx::Bitmap& re
continue;
auto barycentric = FloatVector3(coords.x(), coords.y(), coords.z()) * one_over_area;
float z = interpolate(triangle.vertices[0].z, triangle.vertices[1].z, triangle.vertices[2].z, barycentric);
float z = interpolate(triangle.vertices[0].position.z(), triangle.vertices[1].position.z(), triangle.vertices[2].position.z(), barycentric);
z = options.depth_min + (options.depth_max - options.depth_min) * (z + 1) / 2;
bool pass = false;
@ -322,26 +323,26 @@ static void rasterize_triangle(const RasterizerOptions& options, Gfx::Bitmap& re
// Perspective correct barycentric coordinates
auto barycentric = FloatVector3(coords.x(), coords.y(), coords.z()) * one_over_area;
float interpolated_reciprocal_w = interpolate(triangle.vertices[0].w, triangle.vertices[1].w, triangle.vertices[2].w, barycentric);
float interpolated_reciprocal_w = interpolate(triangle.vertices[0].position.w(), triangle.vertices[1].position.w(), triangle.vertices[2].position.w(), barycentric);
float interpolated_w = 1 / interpolated_reciprocal_w;
barycentric = barycentric * FloatVector3(triangle.vertices[0].w, triangle.vertices[1].w, triangle.vertices[2].w) * interpolated_w;
barycentric = barycentric * FloatVector3(triangle.vertices[0].position.w(), triangle.vertices[1].position.w(), triangle.vertices[2].position.w()) * interpolated_w;
// FIXME: make this more generic. We want to interpolate more than just color and uv
FloatVector4 vertex_color;
if (options.shade_smooth) {
vertex_color = interpolate(
FloatVector4(triangle.vertices[0].r, triangle.vertices[0].g, triangle.vertices[0].b, triangle.vertices[0].a),
FloatVector4(triangle.vertices[1].r, triangle.vertices[1].g, triangle.vertices[1].b, triangle.vertices[1].a),
FloatVector4(triangle.vertices[2].r, triangle.vertices[2].g, triangle.vertices[2].b, triangle.vertices[2].a),
triangle.vertices[0].color,
triangle.vertices[1].color,
triangle.vertices[2].color,
barycentric);
} else {
vertex_color = { triangle.vertices[0].r, triangle.vertices[0].g, triangle.vertices[0].b, triangle.vertices[0].a };
vertex_color = triangle.vertices[0].color;
}
auto uv = interpolate(
FloatVector2(triangle.vertices[0].u, triangle.vertices[0].v),
FloatVector2(triangle.vertices[1].u, triangle.vertices[1].v),
FloatVector2(triangle.vertices[2].u, triangle.vertices[2].v),
triangle.vertices[0].tex_coord,
triangle.vertices[1].tex_coord,
triangle.vertices[2].tex_coord,
barycentric);
*pixel = pixel_shader(uv, vertex_color);