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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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152
Userland/Libraries/LibGL/SoftwareGLContext.cpp
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@ -123,6 +123,9 @@ void SoftwareGLContext::gl_end()
// Make sure we had a `glBegin` before this call...
RETURN_WITH_ERROR_IF(!m_in_draw_state, GL_INVALID_OPERATION);
triangle_list.clear_with_capacity();
processed_triangles.clear_with_capacity();
// Let's construct some triangles
if (m_current_draw_mode == GL_TRIANGLES) {
GLTriangle triangle;
@ -169,29 +172,22 @@ void SoftwareGLContext::gl_end()
triangle_list.append(triangle);
}
} else {
vertex_list.clear_with_capacity();
RETURN_WITH_ERROR_IF(true, GL_INVALID_ENUM);
}
vertex_list.clear_with_capacity();
auto mvp = m_projection_matrix * m_model_view_matrix;
// Now let's transform each triangle and send that to the GPU
for (size_t i = 0; i < triangle_list.size(); i++) {
GLTriangle& triangle = triangle_list.at(i);
GLVertex& vertexa = triangle.vertices[0];
GLVertex& vertexb = triangle.vertices[1];
GLVertex& vertexc = triangle.vertices[2];
FloatVector4 veca({ vertexa.x, vertexa.y, vertexa.z, 1.0f });
FloatVector4 vecb({ vertexb.x, vertexb.y, vertexb.z, 1.0f });
FloatVector4 vecc({ vertexc.x, vertexc.y, vertexc.z, 1.0f });
// First multiply the vertex by the MODELVIEW matrix and then the PROJECTION matrix
veca = m_model_view_matrix * veca;
veca = m_projection_matrix * veca;
vecb = m_model_view_matrix * vecb;
vecb = m_projection_matrix * vecb;
vecc = m_model_view_matrix * vecc;
vecc = m_projection_matrix * vecc;
triangle.vertices[0].position = mvp * triangle.vertices[0].position;
triangle.vertices[1].position = mvp * triangle.vertices[1].position;
triangle.vertices[2].position = mvp * triangle.vertices[2].position;
// At this point, we're in clip space
// Here's where we do the clipping. This is a really crude implementation of the
@ -203,87 +199,35 @@ void SoftwareGLContext::gl_end()
// Okay, let's do some face culling first
Vector<FloatVector4> vecs;
Vector<GLVertex> verts;
m_clipped_vertices.clear_with_capacity();
m_clipped_vertices.append(triangle.vertices[0]);
m_clipped_vertices.append(triangle.vertices[1]);
m_clipped_vertices.append(triangle.vertices[2]);
m_clipper.clip_triangle_against_frustum(m_clipped_vertices);
vecs.append(veca);
vecs.append(vecb);
vecs.append(vecc);
m_clipper.clip_triangle_against_frustum(vecs);
if (m_clipped_vertices.size() < 3)
continue;
// TODO: Copy color and UV information too!
for (size_t vec_idx = 0; vec_idx < vecs.size(); vec_idx++) {
FloatVector4& vec = vecs.at(vec_idx);
GLVertex vertex;
for (auto& vec : m_clipped_vertices) {
// perspective divide
float w = vec.position.w();
vec.position.set_x(vec.position.x() / w);
vec.position.set_y(vec.position.y() / w);
vec.position.set_z(vec.position.z() / w);
vec.position.set_w(1 / w);
// Perform the perspective divide
if (vec.w() != 0.0f) {
vec.set_x(vec.x() / vec.w());
vec.set_y(vec.y() / vec.w());
vec.set_z(vec.z() / vec.w());
vec.set_w(1 / vec.w());
}
vertex.x = vec.x();
vertex.y = vec.y();
vertex.z = vec.z();
vertex.w = vec.w();
// FIXME: This is to suppress any -Wunused errors
vertex.u = 0.0f;
vertex.v = 0.0f;
if (vec_idx == 0) {
vertex.r = vertexa.r;
vertex.g = vertexa.g;
vertex.b = vertexa.b;
vertex.a = vertexa.a;
vertex.u = vertexa.u;
vertex.v = vertexa.v;
} else if (vec_idx == 1) {
vertex.r = vertexb.r;
vertex.g = vertexb.g;
vertex.b = vertexb.b;
vertex.a = vertexb.a;
vertex.u = vertexb.u;
vertex.v = vertexb.v;
} else {
vertex.r = vertexc.r;
vertex.g = vertexc.g;
vertex.b = vertexc.b;
vertex.a = vertexc.a;
vertex.u = vertexc.u;
vertex.v = vertexc.v;
}
vertex.x = (vec.x() + 1.0f) * (scr_width / 2.0f) + 0.0f; // TODO: 0.0f should be something!?
vertex.y = scr_height - ((vec.y() + 1.0f) * (scr_height / 2.0f) + 0.0f);
vertex.z = vec.z();
verts.append(vertex);
// to screen space
vec.position.set_x(scr_width / 2 + vec.position.x() * scr_width / 2);
vec.position.set_y(scr_height / 2 - vec.position.y() * scr_height / 2);
}
if (verts.size() == 0) {
continue;
} else if (verts.size() == 3) {
GLTriangle tri;
GLTriangle tri;
tri.vertices[0] = m_clipped_vertices[0];
for (size_t i = 1; i < m_clipped_vertices.size() - 1; i++) {
tri.vertices[0] = verts.at(0);
tri.vertices[1] = verts.at(1);
tri.vertices[2] = verts.at(2);
tri.vertices[1] = m_clipped_vertices[i];
tri.vertices[2] = m_clipped_vertices[i + 1];
processed_triangles.append(tri);
} else if (verts.size() == 4) {
GLTriangle tri1;
GLTriangle tri2;
tri1.vertices[0] = verts.at(0);
tri1.vertices[1] = verts.at(1);
tri1.vertices[2] = verts.at(2);
processed_triangles.append(tri1);
tri2.vertices[0] = verts.at(0);
tri2.vertices[1] = verts.at(2);
tri2.vertices[2] = verts.at(3);
processed_triangles.append(tri2);
}
}
@ -292,10 +236,10 @@ void SoftwareGLContext::gl_end()
// Let's calculate the (signed) area of the triangle
// https://cp-algorithms.com/geometry/oriented-triangle-area.html
float dxAB = triangle.vertices[0].x - triangle.vertices[1].x; // A.x - B.x
float dxBC = triangle.vertices[1].x - triangle.vertices[2].x; // B.X - C.x
float dyAB = triangle.vertices[0].y - triangle.vertices[1].y;
float dyBC = triangle.vertices[1].y - triangle.vertices[2].y;
float dxAB = triangle.vertices[0].position.x() - triangle.vertices[1].position.x(); // A.x - B.x
float dxBC = triangle.vertices[1].position.x() - triangle.vertices[2].position.x(); // B.X - C.x
float dyAB = triangle.vertices[0].position.y() - triangle.vertices[1].position.y();
float dyBC = triangle.vertices[1].position.y() - triangle.vertices[2].position.y();
float area = (dxAB * dyBC) - (dxBC * dyAB);
if (area == 0.0f)
@ -314,10 +258,6 @@ void SoftwareGLContext::gl_end()
m_rasterizer.submit_triangle(triangle, m_texture_units);
}
triangle_list.clear();
processed_triangles.clear();
vertex_list.clear();
m_in_draw_state = false;
}
@ -546,19 +486,9 @@ void SoftwareGLContext::gl_vertex(GLdouble x, GLdouble y, GLdouble z, GLdouble w
GLVertex vertex;
vertex.x = x;
vertex.y = y;
vertex.z = z;
vertex.w = w;
vertex.r = m_current_vertex_color.x();
vertex.g = m_current_vertex_color.y();
vertex.b = m_current_vertex_color.z();
vertex.a = m_current_vertex_color.w();
// FIXME: This is to suppress any -Wunused errors
vertex.w = 0.0f;
vertex.u = m_current_vertex_tex_coord.x();
vertex.v = m_current_vertex_tex_coord.y();
vertex.position = { static_cast<float>(x), static_cast<float>(y), static_cast<float>(z), static_cast<float>(w) };
vertex.color = m_current_vertex_color;
vertex.tex_coord = { m_current_vertex_tex_coord.x(), m_current_vertex_tex_coord.y() };
vertex_list.append(vertex);
}
@ -847,7 +777,7 @@ void SoftwareGLContext::gl_delete_lists(GLuint list, GLsizei range)
return;
for (auto& entry : m_listings.span().slice(list - 1, range))
entry.entries.clear();
entry.entries.clear_with_capacity();
}
void SoftwareGLContext::gl_end_list()