Billboarding & AlphaBlendTextures

Billboarding & AlphaBlendTextures

lab16-BillboardingTextureShadedQuad

 

yaw
Look

// create a axis-aligned billboard matrix
void buildAxisAlignedBillboardMatrix(glm::mat4& m, glm::vec3& axis)
{
// calculate “-yaw” angle from View matrix (Look.x, Look.z)
float theta = -atan2f(m[0][2], m[2][2]);

float ct = cosf(theta);
float st = sinf(theta);

// normalize
axis = glm::normalize(axis);

// clear out the view matrix passed in
m = glm::mat4(1.0f);

//———————————————
// R = uu’ + cos(theta)*(I-uu’) + sin(theta)*S
//
// S =  0  -z   y    u’ = (x, y, z)
//     z   0  -x
//    -y   x   0
//———————————————
// calculate “Rotation” matrix using “axis” & “theta”
m[0][0] = axis[0] * axis[0] + ct*(1 – axis[0] * axis[0]) ;
m[0][1] = axis[0] * axis[1] + ct*(0 – axis[0] * axis[1]) + st*(-axis[2]);
m[0][2] = axis[0] * axis[2] + ct*(0 – axis[0] * axis[2]) + st*axis[1];

m[1][0] = axis[1] * axis[0] + ct*(0 – axis[1] * axis[0]) + st*axis[2];
m[1][1] = axis[1] * axis[1] + ct*(1 – axis[1] * axis[1]) ;
m[1][2] = axis[1] * axis[2] + ct*(0 – axis[1] * axis[2]) + st*(-axis[0]);

m[2][0] = axis[2] * axis[0] + ct*(0 – axis[2] * axis[0]) + st*(-axis[1]);
m[2][1] = axis[2] * axis[1] + ct*(0 – axis[2] * axis[1]) + st*axis[0];
m[2][2] = axis[2] * axis[2] + ct*(1 – axis[2] * axis[2]) ;
}

Billboard가 활성화가 되지 않은 상태 (카메라의 시점이 회전된 상태에 따라 알파텍스쳐 나무가 원래 위치한대로 그대로 유지함)

 

Billboard가 활성화된 상태 (카메라의 시점이 회전된 상태라 해도 알파텍스쳐 나무가 내 시점을 향하여 바라보는 상태를 유지함)

 

Blending Filter

Blending filter

lab16-BlendFilterTextureShadedQuad

glEnable(GL_BLEND);
if (g_filter == 0) // Default (no blending) = Cs*1
glBlendFunc(GL_ONE, GL_ZERO);
else if (g_filter == 1) // Draw background only = Cd*1
glBlendFunc(GL_ZERO, GL_ONE);
else if (g_filter == 2) // Cs*1 + Cd*1
glBlendFunc(GL_ONE, GL_ONE);
else if (g_filter == 3) // Alpha blending (back-to-front) = Cs*As + Cd*(1-As)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
else if (g_filter == 4) // brighten the scene = Cs*As + Cd*1
glBlendFunc(GL_SRC_ALPHA, GL_ONE);
else if (g_filter == 5) // Modulate blending = Cd*Cs
glBlendFunc(GL_ZERO, GL_SRC_COLOR);
else if (g_filter == 6) // darken the scene = Cd*As
glBlendFunc(GL_ZERO, GL_SRC_ALPHA);
else if (g_filter == 7) // Invert all the colors = Cs*(1-Cd)
glBlendFunc(GL_ONE_MINUS_DST_COLOR, GL_ZERO);
Default (no blending)
noblending

Draw background only

backgroundonly

Add blending

addblending

Alpha blending

alphablending

Brighten the scene

additiveblending

Modulate blending

modulateblending

Darken the scene

darken

Invert all the colors

invert

TextureShadedQuad-FilteringWrappingAnimation

lab14-TextureShadedQuad-FilteringWrappingAnimation

animatedTexture (flipbook animation)

animatedTexture

texture filtering
// LL mag nearest – min nearest
// LR mag linear – min linear
// UL mag linear – min linear – mipmap nearest
// UR mag linear – min linear – mipmap linear

textureFiltering

texture wrapping – texCoords LL(-1, -1), LR(3, -1), UL(-1, 3), UR(3, 3)
// LL CLAMP
// LR CLAMP_TO_EDGE
// UL REPEAT
// UR MIRRORED_REPEAT
textureWrapping

TextureShadedGeometry

lab13-TextureShadedGeometry

Texture2D 클래스 사용한 Texture Mapping 정의

GeometryPositionNormalTexture 클래스 사용

‘g’-key 사용, Texture Pyramid->Cube->Sphere->Cylinder->Torus->Parallelepiped->Grid 변환

Pyramid

void Cone::init()
{
numVertices = 0;
glm::vec3 n(0.0f, 0.0f, 0.0f);
float xTexCoord = 0.0f;
float dslice = 1.0f / slices;

float theta = (float)(2 * M_PI / slices);
for (int i = 0; i < slices; i++)
{
glm::vec3 v1, v2, v3;
// V1
v1[0] = p[0];
v1[1] = p[1] + height;
v1[2] = p[2];
// V2
v2[0] = p[0] + radius * cosf(theta * i);
v2[1] = p[1];
v2[2] = p[2] + radius * sinf(theta * i);
// V3
v3[0] = p[0] + radius * cosf(theta * ((i + 1) % slices));
v3[1] = p[1];
v3[2] = p[2] + radius * sinf(theta * ((i + 1) % slices));
// Normal
glm::vec3 n = glm::cross((v2-v1), (v3-v1));
n = glm::normalize(n);
printf(“V1: %f %f %f\n”, v1[0], v1[1], v1[2]);
printf(“V2: %f %f %f\n”, v2[0], v2[1], v2[2]);
printf(“V3: %f %f %f\n”, v3[0], v3[1], v3[2]);
printf(“N: %f %f %f\n\n”, n[0], n[1], n[2]);

// V1
vbo.addData(&v1, sizeof(glm::vec3)); // vertex position
vbo.addData(&glm::vec2(xTexCoord + dslice * 0.5f, 1.0f), sizeof(glm::vec2)); // vertex texture coordnate (TopCenter)
vbo.addData(&n, sizeof(glm::vec3)); // vertex normal
// V2
vbo.addData(&v2, sizeof(glm::vec3)); // vertex position
vbo.addData(&glm::vec2(xTexCoord, 0.0f), sizeof(glm::vec2)); // vertex texture coordnate
vbo.addData(&n, sizeof(glm::vec3)); // vertex normal
// V3
vbo.addData(&v3, sizeof(glm::vec3)); // vertex position
vbo.addData(&glm::vec2(xTexCoord + dslice, 0.0f), sizeof(glm::vec2)); // vertex texture coordnate
vbo.addData(&n, sizeof(glm::vec3)); // vertex normal

xTexCoord += dslice; // increment texCoord
numVertices += 3;
}

createVAO();
isLoaded = true;
}