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implement perspective correct interpolation to the 2D window space clipped brush stroke sample.

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This commit is contained in:
omigamedev
2018-11-15 18:09:19 +01:00
parent 18067726b5
commit 8f9422b6d6
5 changed files with 162 additions and 22 deletions
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91
src/canvas.cpp
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@@ -423,15 +423,29 @@ void ui::Canvas::stroke_draw()
+ dx + dy, // C - top-right
+ dx - dy, // D - bottom-right
};
static glm::vec4 P[4];
int intersected = 0;
int inside = 0;
// face is the 2d shape of the cube plane i projected onto the window space
auto face = face_to_shape2D(i);
// P is the initial square centered at the cursor location
std::vector<vertex_t> P{
vertex_t{ {0, 0, 1, 1}, {0, 0}, {0, 0} },
vertex_t{ {0, 0, 1, 1}, {0, 1}, {0, 1} },
vertex_t{ {0, 0, 1, 1}, {1, 1}, {1, 1} },
vertex_t{ {0, 0, 1, 1}, {1, 0}, {1, 0} },
};
for (int j = 0; j < 4; j++)
P[j].pos = glm::vec4(xy(s.pos) + off[j] * glm::orientate2(-s.angle), 1, 1);
// intersect P with the current face to clip diverging points from the plane
P = poly_intersect(P, face);
for (int j = 0; j < P.size(); j++)
{
glm::vec3 ray_origin, ray_dir;
if (s.pos.z == 0)
{
point_unproject(xy(s.pos) + off[j] * glm::orientate2(-s.angle), { 0, 0, zw(m_box) }, m_mv, m_proj, ray_origin, ray_dir);
point_unproject(P[j].pos, { 0, 0, zw(m_box) }, m_mv, m_proj, ray_origin, ray_dir);
}
else
{
@@ -451,19 +465,29 @@ void ui::Canvas::stroke_draw()
{
inside++;
}
P[j].x = -(plane_local.x * 0.5f - 0.5f) * m_width;
P[j].y = (plane_local.y * 0.5f + 0.5f) * m_height;
P[j].pos.x = -(plane_local.x * 0.5f - 0.5f) * m_width;
P[j].pos.y = (plane_local.y * 0.5f + 0.5f) * m_height;
P[j].uvs2 = UV2[j];
// Black magic - BEWARE!
// interpolation perspective correction, use the current camera projection to correct the interpolation
// because the new shape will have z fixed with an ortho projection when drawn to the face
// we need to imitate the same perspective as the once in the camera
// see: https://www.scratchapixel.com/lessons/3d-basic-rendering/rasterization-practical-implementation/perspective-correct-interpolation-vertex-attributes
auto hit_cam = m_mv * glm::vec4(hit, 1);
P[j].pos.z = hit_cam.z;
P[j].uvs *= hit_cam.z;
P[j].uvs2 *= hit_cam.z;
intersected++;
}
else
{
// if (i==0)
// LOG("no intersection with plane %d", i);
break;
}
}
if (intersected < 4 || inside == 0)
if (intersected < 3 || inside == 0)
continue;
m_dirty_face[i] = true;
@@ -473,13 +497,12 @@ void ui::Canvas::stroke_draw()
glActiveTexture(GL_TEXTURE1);
m_tex[i].bind(); // bg, copy of framebuffer (copied before drawing)
glm::vec2 bb_min(m_width, m_height);
glm::vec2 bb_max(0, 0);
for (int j = 0; j < 4; j++)
for (int j = 0; j < P.size(); j++)
{
bb_min = glm::max({ 0, 0 }, glm::min(bb_min, xy(P[j])));
bb_max = glm::min({ m_width, m_height }, glm::max(bb_max, xy(P[j])));
bb_min = glm::max({ 0, 0 }, glm::min(bb_min, xy(P[j].pos)));
bb_max = glm::min({ m_width, m_height }, glm::max(bb_max, xy(P[j].pos)));
}
auto bb_sz = bb_max - bb_min;
@@ -498,11 +521,41 @@ void ui::Canvas::stroke_draw()
glm::max(zw(m_dirty_box[i]), (glm::vec2)(tex_pos + tex_sz))
);
ShaderManager::use(ui::kShader::Stroke);
ShaderManager::u_mat4(kShaderUniform::MVP, ortho_proj);
ShaderManager::u_vec4(kShaderUniform::Col, glm::vec4(s.col, m_brush.m_tip_color.a));
ShaderManager::u_float(kShaderUniform::Alpha, s.flow);
m_plane_brush.update_vertices(P, nullptr, UV2);
m_plane_brush.draw_fill();
P = triangulate_simple(P);
m_brush_shape.update_vertices(P.data(), P.size());
m_brush_shape.draw_fill();
/*
// draw sample wireframe
std::vector<vertex_t> lines;
for (int vi = 0; vi < P.size(); vi += 3)
{
auto a = P[vi];
auto b = P[(vi + 1) % P.size()];
auto c = P[(vi + 2) % P.size()];
a.pos.z = b.pos.z = c.pos.z = 0;
lines.push_back(a);
lines.push_back(b);
lines.push_back(b);
lines.push_back(c);
lines.push_back(c);
lines.push_back(a);
}
ShaderManager::use(kShader::Color);
ShaderManager::u_vec4(kShaderUniform::Col, { s.col, 1 });
ShaderManager::u_mat4(kShaderUniform::MVP, ortho_proj);
m_brush_shape.update_vertices(lines.data(), lines.size());
m_brush_shape.draw_stroke();
*/
glActiveTexture(GL_TEXTURE1);
m_tex[i].unbind();
@@ -950,6 +1003,7 @@ bool ui::Canvas::create(int width, int height)
m_sampler_mix.create(GL_NEAREST, GL_REPEAT);
m_plane.create<1>(1, 1);
m_plane_brush.create<1>(1, 1);
m_brush_shape.create();
m_mesh.create();
m_brush_mix.create(8, 8);
for (auto& l : m_layers)
@@ -2039,8 +2093,8 @@ std::vector<glm::vec2> ui::Canvas::face_to_shape2D(int plane_index)
{
auto pt_clip = m_proj * glm::vec4(p, 1);
pt_clip = pt_clip / pt_clip.w;
glm::vec2 pt_screen = (glm::vec2(pt_clip) * glm::vec2(1,-1) * 0.5f + 0.5f) * zw(m_vp);
//pt_screen.y = m_vp.w - pt_screen.y - 1;
glm::vec2 pt_screen = (glm::vec2(pt_clip) * 0.5f + 0.5f) * zw(m_vp);
pt_screen.y = m_vp.w - pt_screen.y - 1;
points.push_back(pt_screen);
}
return points;
@@ -2065,11 +2119,8 @@ std::vector<vertex_t> ui::Canvas::triangulate_simple(const std::vector<vertex_t>
vertex_t vertex;
for (int i = 0; i < 3; i++)
{
auto p = t->GetPoint(i);
auto index = std::distance(points.data(), p);
vertex.pos = glm::vec4(p->x, p->y, 0, 1);
vertex.uvs = vertices[index].uvs;
ret.push_back(vertex);
auto index = std::distance(points.data(), t->GetPoint(i));
ret.push_back(vertices[index]);
}
}