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LibGL+LibSoftGPU: Move primitive assembly and clipping into LibSoftGPU

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Stephan Unverwerth 2021-12-16 21:26:15 +01:00 • committed by Brian Gianforcaro
parent 2f35135743
commit 73ba208ee7
4 changed files with 176 additions and 161 deletions
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163
Userland/Libraries/LibGL/SoftwareGLContext.cpp
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@ -208,175 +208,32 @@ void SoftwareGLContext::gl_end()
{
APPEND_TO_CALL_LIST_AND_RETURN_IF_NEEDED(gl_end);
// At this point, the user has effectively specified that they are done with defining the geometry
// of what they want to draw. We now need to do a few things (https://www.khronos.org/opengl/wiki/Rendering_Pipeline_Overview):
//
// 1. Transform all of the vertices in the current vertex list into eye space by mulitplying the model-view matrix
// 2. Transform all of the vertices from eye space into clip space by multiplying by the projection matrix
// 3. If culling is enabled, we cull the desired faces (https://learnopengl.com/Advanced-OpenGL/Face-culling)
// 4. Each element of the vertex is then divided by w to bring the positions into NDC (Normalized Device Coordinates)
// 5. The vertices are sorted (for the rasteriser, how are we doing this? 3Dfx did this top to bottom in terms of vertex y coordinates)
// 6. The vertices are then sent off to the rasteriser and drawn to the screen
float scr_width = m_frontbuffer->width();
float scr_height = m_frontbuffer->height();
// Make sure we had a `glBegin` before this call...
RETURN_WITH_ERROR_IF(!m_in_draw_state, GL_INVALID_OPERATION);
m_in_draw_state = false;
triangle_list.clear_with_capacity();
processed_triangles.clear_with_capacity();
// FIXME: Add support for the remaining primitive types.
if (m_current_draw_mode != GL_TRIANGLES
&& m_current_draw_mode != GL_TRIANGLE_FAN
&& m_current_draw_mode != GL_TRIANGLE_STRIP
&& m_current_draw_mode != GL_QUADS
&& m_current_draw_mode != GL_POLYGON) {
// Let's construct some triangles
if (m_current_draw_mode == GL_TRIANGLES) {
GLTriangle triangle;
for (size_t i = 0; i < vertex_list.size(); i += 3) {
triangle.vertices[0] = vertex_list.at(i);
triangle.vertices[1] = vertex_list.at(i + 1);
triangle.vertices[2] = vertex_list.at(i + 2);
triangle_list.append(triangle);
}
} else if (m_current_draw_mode == GL_QUADS) {
// We need to construct two triangles to form the quad
GLTriangle triangle;
VERIFY(vertex_list.size() % 4 == 0);
for (size_t i = 0; i < vertex_list.size(); i += 4) {
// Triangle 1
triangle.vertices[0] = vertex_list.at(i);
triangle.vertices[1] = vertex_list.at(i + 1);
triangle.vertices[2] = vertex_list.at(i + 2);
triangle_list.append(triangle);
// Triangle 2
triangle.vertices[0] = vertex_list.at(i + 2);
triangle.vertices[1] = vertex_list.at(i + 3);
triangle.vertices[2] = vertex_list.at(i);
triangle_list.append(triangle);
}
} else if (m_current_draw_mode == GL_TRIANGLE_FAN || m_current_draw_mode == GL_POLYGON) {
GLTriangle triangle;
triangle.vertices[0] = vertex_list.at(0); // Root vertex is always the vertex defined first
for (size_t i = 1; i < vertex_list.size() - 1; i++) // This is technically `n-2` triangles. We start at index 1
{
triangle.vertices[1] = vertex_list.at(i);
triangle.vertices[2] = vertex_list.at(i + 1);
triangle_list.append(triangle);
}
} else if (m_current_draw_mode == GL_TRIANGLE_STRIP) {
GLTriangle triangle;
for (size_t i = 0; i < vertex_list.size() - 2; i++) {
triangle.vertices[0] = vertex_list.at(i);
triangle.vertices[1] = vertex_list.at(i + 1);
triangle.vertices[2] = vertex_list.at(i + 2);
triangle_list.append(triangle);
}
} else {
vertex_list.clear_with_capacity();
m_vertex_list.clear_with_capacity();
dbgln_if(GL_DEBUG, "gl_end: draw mode {:#x} unsupported", m_current_draw_mode);
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);
// First multiply the vertex by the MODELVIEW matrix and then the PROJECTION matrix
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;
// Apply texture transformation
// FIXME: implement multi-texturing: texcoords should be stored per texture unit
triangle.vertices[0].tex_coord = m_texture_matrix * triangle.vertices[0].tex_coord;
triangle.vertices[1].tex_coord = m_texture_matrix * triangle.vertices[1].tex_coord;
triangle.vertices[2].tex_coord = m_texture_matrix * triangle.vertices[2].tex_coord;
// At this point, we're in clip space
// Here's where we do the clipping. This is a really crude implementation of the
// https://learnopengl.com/Getting-started/Coordinate-Systems
// "Note that if only a part of a primitive e.g. a triangle is outside the clipping volume OpenGL
// will reconstruct the triangle as one or more triangles to fit inside the clipping range. "
//
// ALL VERTICES ARE DEFINED IN A CLOCKWISE ORDER
// Okay, let's do some face culling first
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);
if (m_clipped_vertices.size() < 3)
continue;
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);
// 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);
}
GLTriangle tri;
tri.vertices[0] = m_clipped_vertices[0];
for (size_t i = 1; i < m_clipped_vertices.size() - 1; i++) {
tri.vertices[1] = m_clipped_vertices[i];
tri.vertices[2] = m_clipped_vertices[i + 1];
processed_triangles.append(tri);
}
}
m_bound_texture_units.clear();
for (auto& texture_unit : m_texture_units) {
if (texture_unit.is_bound())
m_bound_texture_units.append(texture_unit);
}
for (size_t i = 0; i < processed_triangles.size(); i++) {
GLTriangle& triangle = processed_triangles.at(i);
m_rasterizer.draw_primitives(m_current_draw_mode, m_projection_matrix * m_model_view_matrix, m_texture_matrix, m_vertex_list, m_bound_texture_units);
// Let's calculate the (signed) area of the triangle
// https://cp-algorithms.com/geometry/oriented-triangle-area.html
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)
continue;
if (m_cull_faces) {
bool is_front = (m_front_face == GL_CCW ? area < 0 : area > 0);
if (is_front && (m_culled_sides == GL_FRONT || m_culled_sides == GL_FRONT_AND_BACK))
continue;
if (!is_front && (m_culled_sides == GL_BACK || m_culled_sides == GL_FRONT_AND_BACK))
continue;
}
if (area > 0) {
swap(triangle.vertices[0], triangle.vertices[1]);
}
m_rasterizer.submit_triangle(triangle, m_bound_texture_units);
}
m_vertex_list.clear_with_capacity();
}
void SoftwareGLContext::gl_frustum(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble near_val, GLdouble far_val)
@ -650,7 +507,7 @@ void SoftwareGLContext::gl_vertex(GLdouble x, GLdouble y, GLdouble z, GLdouble w
vertex.tex_coord = m_current_vertex_tex_coord;
vertex.normal = m_current_vertex_normal;
vertex_list.append(vertex);
m_vertex_list.append(vertex);
}
// FIXME: We need to add `r` and `q` to our GLVertex?!